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So we now know what containers are,

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and that Docker helps us create these containers.

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I also already outlined some advantages.

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But still, you might wonder,

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why exactly do we need containers in software development?

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Maybe the example made sense for a picnic basket?

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And to some extent, it makes sense

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for a software development.

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But is it really that important that useful?

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Yes, it is, we should just ask ourselves

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one simple question.

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Why would we want independent standardized application

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packages in software development?

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Well, for one, one very good and typical example.

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And one of the main use cases of Docker,

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I would say, We of course, often have different development

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and production environments.

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And here's a simple example.

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Let's say you created a Node.js application.

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And you wrote some code there,

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which requires Node.js version 14.3

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to run successfully.

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And this is not some made up example.

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The example you see here is Node.js code,

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which uses a feature called top level await.

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Now you don't need to know Node.js to follow along

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with this course, for the moment, it's enough to know that

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this is a feature, which would not work

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in older versions of Node.js .

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We need Node.js 14.3 or higher to execute

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this code successfully.

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The problem is that we might have that version installed

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on our local environment, on our development environment,

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on our local machine.

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But if we then take this application,

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and we deploy it onto some remote machine onto a server,

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where it should be hosted, so that the entire world

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can reach it, then on that remote machine,

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we might have an older version of Node.js installed,

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maybe 14.1, or 12, or eight, whatever.

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And all of a sudden, the code which worked locally

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on our machine doesn't work there anymore.

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And depending on what's going wrong,

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it can take quite some time to figure out what

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the problem was.

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So having the same and with that,

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I really mean, the exact same development environment,

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as we have it in production can be worth a lot.

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And that is something where Docker

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and containers can help you,

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you can lock a specific Node version

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into your Docker container, and therefore ensure

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that your code is always executed with that exact version.

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And all of a sudden, that potential problem is gone

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and can't occur anymore.

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Because your application runs in that container,

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which brings its own Node.js version.

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So that's one example.

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Kind of related to that would be another example,

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different development environments within a team

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or a company.

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Let's say we're in a big team.

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I'm working there, and you are working there.

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And now we're working on the same project,

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for example, that same Node.js application again.

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Now because you haven't worked with Node for some time,

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or because you didn't need to update,

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you still have an older version of Node.js installed

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on your system.

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And I have the latest version.

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So I wrote this code with top level await.

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And when I share the code with you,

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it doesn't work for you.

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Now, obviously, you might say,

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updating Node.js is no problem,

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I can easily update it on my system.

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And we're on the same page again.

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Yes, but for one, it's just one example.

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There could be more complex projects with more complex

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dependencies which you need to manage and install.

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And in addition, even in that, one example,

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it's still annoying that we're not able to work on the same

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code base together, and we have some guarantee

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that it will always work.

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And that we always use the same environment.

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We want that reproducibility in software development,

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and therefore even here, if we're not deploying

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it at the moment, having that locked in environment

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with everything the code needs in the container

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can be worth a lot.

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And now last but not least, even if you're working

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on your own, then still Docker and containers

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could be very useful.

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Because if you have multiple projects on which you're

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working, then you might have clashing versions.

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Let's say one project uses Python version two still

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for whatever reason, another project uses the latest

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version of Python.

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The same maybe with Node.js or PHP

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or whatever kinds of projects.

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There you would have clashing versions,

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and that means that whenever you switch

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from project A to project B, you have to uninstalled

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the wrong version and install the right version.

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For example, if one project needs Node version 12,

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the other project needs Node version 14.

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If you switch project, you have to uninstalled version 14

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installed version 12 instead, and vice versa.

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So switching between projects becomes a big hassle,

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and is no fun at all.

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And that, again is something where Docker

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and containers can help us.

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We lock our versions into the containers,

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and every project has its own container.

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And therefore if we then switch projects,

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it'll just work like that.

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We don't need to uninstall and reinstall anything

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because it's all in the container,

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not globally on our host machine.

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And they have first switching projects becomes as easy

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as launching a different container.

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And these are all things we're going to see throughout

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this course.

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And you're going to learn everything you need to solve these

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problems throughout the course.

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And that's why we might wanna consider working

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with containers and why Docker is quite helpful tool.