Configuration files for servers and daemons (like sendmail, cron, apache, privoxy etc) are usually so well commented, that more than 80% of the configuration file is taken up by comments, explaining how you should use the remaining 20%!

Manual pages are invoked with the $man command.

$ man ls
gives the manual page of “ls”. There are different sections of manual pages, depending on what kind of perspective you have.
Try:
$ man 2 reboot
$ man 8 reboot