How to use man for manual in linux?

if you want to see the ls command's usage.

$ man ls
$ ls --help

Usually man pages are saved in /usr/man or /usr/share/man.

contents of man page are regular. it consists of name, synopsis, description, example and See Also.

for more information refer to:
http://www.ibm.com/developerworks/aix/library/au-spunix_manpages/index.html