Karl Berry Olaf Bachmann and many others. The Quick Help commands are detailed below. Many Ediff commands take numeric prefix arguments.
Some commands take negative prefix arguments as well.
For instance, typing - and then j will make the last difference region current. Typing -2 then j makes the penultimate difference region current, etc. Without the prefix argument, all commands operate on the currently selected difference region. You can make any difference region current using the various commands explained below. For some commands, the actual value of the prefix argument is immaterial.