In this section we comment only on the features that cannot be readily deduced from the quick help window. You can always type E in the control window to display this manual. Many Ediff commands take numeric prefix arguments.
Some commands take negative prefix arguments as well.
For instance, typing - and then j will take Ediff to the last difference. Typing -2 then j takes Ediff to to the penultimate difference region, etc. Without the prefix argument, all commands operate on the current selected difference region. You can select any difference region as the current one using other Ediff commands. For some commands, the value of the prefix argument is immaterial.