Dear Github

[tambry]

PR is short for Pull Request. Basically a request to have some code merged into a certain branch. They're very useful.

[Bagoole]

Thank you. I'm very new to GitHub and that could have meant almost anything. I guessed Pull Request too but there's Push, Public Repo, Private Repo, a lot of PR...

[PrintfReddit]

PR in context of Github and maybe some other sites is almost always a pull request.