Looking up things with Vim's :help command can be error prone if you don't
know exactly how to format what you are looking up. Bypass some of the
guesswork by hitting Ctrl-d after writing part of the :help command.
This will populate a wildmenu of possible matches.
For instance, if you know there is a command containing ?, but you aren't
sure how to look it up, try the following:
:help ?<Ctrl-d>
You can tab through to the one you want and hit enter to read up on it. Who
knew there were so many Vim bindings involving a ?.
See :h help-context for more details.