The checkout command moves you off the experimental branch and back onto the master branch.

The merge command then takes the commits in experimental that aren't in master and puts them into master.

Thanks, I think I may have been misusing

    git branch [some name]

I'll take a look at some of the suggested tutorials again. Thanks all. That said, I pretty much do straight-ahead main-line development, so this isn't a huge problem right now. I do most of my development after midnight, so there isn't a huge cognitive headroom left...