To get an overview of section 1 (one) of the manual:
man 1 intro
This section deals with user commands: the commands you are most likely to use.
To search the online manual for a command with the keyword "mail":
man -k mail
This displays a one line synopsis of each command that has this keyword in its description.
To search the online manual for a command with the phrase "copy files":
man -k 'copy files'
This displays a one line synopsis for each command that has this phrase in its description.
To check what a command does:
whatis more more, page (1) - browse or page through a text file
This displays a one line description of what the command does.
To display the manual page for the cp (copy files) command:
--More--48% at the bottom left of the screen means that only 48% of the man page is displayed.
Press the space bar to display more of it or type q to quit.
To print the manual page for the man command:
man -t man
This prints the manual page to your default printer.