In Quick Man Pages, I explained how you can quickly
open man pages with K. For times when the particular command isn't in the
buffer or the command contains a hyphen, you can instead use :Man. With
the ft-man-plugin enabled, you can use :Man with the name of any command
that has a manual page and the respective man page will be opened in a split
buffer. For example, check out git log with:
:Man git-log
If you don't want the first manual entry, provide a specific number. For
instance, you can open the echo(3) man page with:
:Man 3 echo
See :h :Man for more details.