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 of interest; for
example, C-h k C-n tells you 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 Help.