A Git submodule is a repository that is embedded inside another repository at a specific path. In other words, a submodule is a way to incorporate the contents of one Git repository into another Git repository as a subdirectory.
Submodules allow you to keep a separate repository for a specific project or component of your code, while still being able to reference it from within your main repository. This can be useful, for example, when you want to use a third-party library or component in your project, but want to keep it separate from your codebase.
When you add a submodule to your repository, Git records the commit hash of the submodule repository in your main repository. This means that when someone clones your main repository, they will also get a reference to the submodule repository at the specific commit you recorded.
To work with submodules, you use Git commands like git submodule add, git submodule update, git submodule init, and git submodule sync. The git submodule add command is used to add a new submodule to your repository. The git submodule update command is used to update the submodule to the latest commit of its branch. The git submodule init command is used to initialize the submodule, and the git submodule sync command is used to synchronize changes to the submodule URL.
Submodules can be a powerful tool when working with large, complex projects that have many interdependent parts. However, they can also be complex and require some care to use correctly. It is important to thoroughly understand how submodules work and how to manage them before using them in a project.