If you forget what a key does, you can find out with the Help
character, which is C-h (or F1, which is an alias for
C-h). Type C-h k followed by the key you want to know
about; for example, C-h k C-n tells you all about what C-n
does. C-h is a prefix key; C-h k is just one of its
subcommands (the command describe-key). The other subcommands of
C-h provide different kinds of help. Type C-h twice to get
a description of all the help facilities. See section Help.