Claude Code is a CLI (Command Line Interface) and thus runs in a terminal.
WHICH terminal is up to you, but the exact usage & keyboard shortcuts will differ, depending on which platform (Windows, macOS, Linux) and terminal you are using.
Therefore, you should consult the official documentation for a complete overview of supported shortcuts and terminal configuration instructions for different terminals / platforms.
For example, entering a line break will be different, depending on which terminal / platform you're using: It may be SHIFT + ENTER or OPTION + ENTER / ALT + ENTER or something else - hence the links above, which list all common platforms / terminals and their shortcuts and "quirks".