Emacs provides extensive help features, all accessible through the help character, C-h. This is a prefix key that is used for commands that display documentation; the next character you type should be a help option, to ask for a particular kind of help. You can cancel the C-h command with C-g. The function key <F1> is equivalent to C-h.
C-h itself is one of the help options; C-h C-h displays
a list of help options, with a brief description of each one
help-for-help). You can scroll the list with <SPC> and
<DEL>, then type the help option you want. To cancel, type
C-h or <F1> means “help” in various other contexts as well. For instance, you can type them after a prefix key to display a list of the keys that can follow the prefix key. (A few prefix keys don't support C-h in this way, because they define other meanings for it, but they all support <F1> for help.)
Most help buffers use a special major mode, Help mode, which lets you scroll conveniently with <SPC> and <DEL>. You can also follow hyperlinks to URLs, and to other facilities including Info nodes and customization buffers. See Help Mode.
If you are looking for a certain feature, but don't know what it is called or where to look, we recommend three methods. First, try an apropos command, then try searching the manual index, then look in the FAQ and the package keywords.