If you forget what a key does, you can find out by typing C-h
describe-key), followed by the key of interest; for
example, C-h k C-n tells you what C-n does.
The prefix key C-h stands for “help”. The key
serves as an alias for C-h. Apart from C-h k, there are
many other help commands providing different kinds of help.
See Help, for details.