Sorry to be clueless but what do Github, Bitbucket and Gitlab do?
The short answer is they host software projects for programmers.
They store previous versions of the files, make it easy for others around the world to find and download the project, contribute changes, file bug reports, etc...
The left has decided that there are too many male, especially white male, programmers and that the only possible explanation is men are scaring away all the women. It has nothing to do with few women having an interest in programming.
GitHub has even stopped calling itself a meritocracy because it hurts the feelings of women and minorities who haven’t succeeded in software development.
They are essentially online services that allow programmers to store/share source code of projects that they are working on. A lot of the shared libraries that a bunch of software depends on are shared via Github, and it is the primary place folks go to file bug reports on said software or request new functionality.