What it does: pick out the GitHub projects that are already packaged and ready to install, group them by what they do and which platforms they support, and put each project's installers, older versions and SHA256 checksums in one place, so you do not have to page through a Releases list hunting for the file that matches your system.
It also handles two things GitHub itself does not: download speed, by rewriting links through mirror sources so you are not waiting on a direct connection to time out; and rollback, so when a version breaks something you can drop back one release without digging through old tags.
No installer files are stored here. Every download resolves to the original GitHub Release URL or a mirror forward. Copyright stays with each repository's author.