I sometimes come across this kind of note on a TAB...

12r (or any other number)

but I dunno how to play that.

Any help is appreicated by this noob
It means you release a bend. there should be something like a 10b in front of it. You don't even really use the 12th fret. You just bend the 10 to sound like a 12 and release it back to a 10. It took me a while to figure that out too
just looked at the tabs. it means you play the 12th fret already bent and release it
no problem man. I remember how tough it was to read tabs at first. Took my friend like a month to teach me. Haha.