Once you have one or a few submodules added, you will notice a new file named
.gitmodules inside your repository. This is a configuration file which holds all information about what you've pulled from where. The content of
.gitmodules should look something like this :
[submodule "requests"] path = requests url = https://github.com/psf/requests.git
The file may contain more entries as you add more submodules.
You should keep in mind that
gitmodules is version-controlled along with the rest of your repository. Anyone who clone/fork from you should be able to access your submodules as well.