Vim is my favourite text editor. It takes a bit of a learning curve to get used to its quirks but it is time well spent if you are doing lots of stuff on the command line or don’t have access to a GUI. I never used emacs so I won’t go into the editor war.
Macros in vim allow to record a sequence of commands and play them back in one go. Here is a cheat sheet adapted from vim tips:
qa start recording to register a
... enter a sequence of commands
q stop recording
@a execute the macro
@@ execute the macro again
Macros allow to automate complex sequences of vim commands and there is much more to it than this simple cheat sheet. Practical Vim dedicates a full chapter to the subject and it’s a good place to start if you want to delve into the magic world of vim macros.