What is the meaning of revert this commit and roll back this commit in GitHub for Windows?

Question

Github for Windows features these two commands described as:

1. revert this commit - create a new commit that reverts the changes of this commit

Answer 1

Is it possible to revert to a previous commit check it out and if I don't like it, go back to where it was initially?

It is now (March 2013), with GitHub for Windows, you can undo a rollback without having to type any git command:

See "Undo Button in GitHub for Windows"

we've added Undo support for Discards, Commits, Rollbacks, and Merges: