help

help
The most import thing to learn about in vim is...

:help
and

:help command
TAB - cycles through possible command completions
CTRL-d - lists possible command completions
For example, try

:help tags (then CTRL-d and TAB)
Do help i_ CTRL-d for insert commands, v_ for visual, etc.

Also, when in the help pages, CTRL-] jumps to subjects between |bars| and CTRL-T jumps back (and, of course, :q to quit).

If you saw ^I (ctrl-I) showed up when you hit the TAB key for auto completion, try to:
:set nocompatible

to solve the ^I problem.