Emacs records a list of changes made in the buffer text, so you can
undo recent changes. This is done using the
which is bound to C-/ (as well as C-x u and C-_).
Normally, this command undoes the last change, moving point back to
where it was before the change. The undo command applies only to
changes in the buffer; you can't use it to undo cursor motion.
Although each editing command usually makes a separate entry in the undo records, very simple commands may be grouped together. Sometimes, an entry may cover just part of a complex command.
If you repeat C-/ (or its aliases), each repetition undoes another, earlier change, back to the limit of the undo information available. If all recorded changes have already been undone, the undo command displays an error message and does nothing.
To learn more about the
undo command, see Undo.