Just a note, but ':help' doesn't always go to what you want. For example the option 'smartindent' (set with ':set smartindent') can be abbreviated as ':set si', but ':help si' takes you to the help for the ':sim[alt]' command.
It's useful to note that when searching through help you type something like:
:help 'si'
To get help on a variable and:
:help :si
To get help on a command. The first form would take you to the help entry for 'smartindent' and the second would take you to the entry for :simalt. If you just use:
:help si
It will just find the first match for 'si', which in this case is the tag :si and not the tag 'si'.
Other possible confusions with :help are:
:help tab
Will take to the help for (the tab key/tab character), whereas the help page for all the things related to Vim tabs is:
:help tabpage
(though :help tabs will take you to the :tabs command which is part of the tabpage help doc)