how to use man page in linux?

#man $command

Type man followed by a command (for which you want help) and start reading. Press
q to quit the manpage. Some man pages contain examples (near the end).

paul@laika:~$ man whois
Reformatting whois(1), please wait...

#man $configfile
Most configuration files have their own manual.
paul@laika:~$ man syslog.conf
Reformatting syslog.conf(5), please wait...

#man $daemon
This is also true for most daemons (background programs) on your system..
paul@laika:~$ man syslogd
Reformatting syslogd(8), please wait...

#man -k (apropos)
man -k (or apropos) shows a list of man pages containing a string.
paul@laika:~$ man -k syslog
lm-syslog-setup (8) - configure laptop mode to switch syslog.conf ...
logger (1) - a shell command interface to the syslog(3) ...
syslog-facility (8) - Setup and remove LOCALx facility for sysklogd
syslog.conf (5) - syslogd(8) configuration file
syslogd (8) - Linux system logging utilities.
syslogd-listfiles (8) - list system logfiles

#whatis
To see just the description of a manual page, use whatis followed by a string.
paul@u810:~$ whatis route
route (8) - show / manipulate the IP routing table

#whereis
The location of a manpage can be revealed with whereis.
paul@laika:~$ whereis -m whois
whois: /usr/share/man/man1/whois.1.gz
This file is directly readable by man.
paul@laika:~$ man /usr/share/man/man1/whois.1.gz