There's also the virtual streams (branches). A mapped overlay over the actual contents of the repo, which you can check out and get a subset of the contents. Or even can provide different files that have been mapped in the server for each particular virtual branch.

This is used so e.g. an artist gets a repo that contains sources for the art assets, while a programmer gets the same repo but instead of art sources, it downloads the already produced binaries. As a SE, you just want to build the code, and don't care about 800 GB of art asset sources.