Linux Man pages are one of the most useful resources a Linux user has in his arsenal when it comes to learning about a command line functionality or just about anything you could need to know about Linux. For example, today I want to transfer some log files from my server to my main computer analysis but a small script I had written, I decided do this via ftp (just cause I could). So the first thing that I did was check the man page to ensure I used the correct commands, by using man ftp.
man ftp
This shows an interactive document. You can scroll down to read more, press q to exit.
There are many different sections to the man program, each containing a different subset of commands and programs. This allows for different documentation of similar or the same named programs. For example, the apt program has to expansions – annotation processing tool and advanced packaging tool. Usually typing in a command into man produces the output you want, sometimes though you have to go searching.
man apt
This gives the man page for annotation processing tool.
man 8 apt
This gives the man page for advanced packaging tool.
If you come across the someone else referencing a man page, or you yourself want to reference a man page you would write it man program(section) eg for advanced packaging tool you would use man apt(8)
The Secret Life of an Undergrad 