man

man stands for "manual" and is a command which presents the "man pages" for a particular command.

What are "man pages"? Man pages are text documents that describe the utility or command, what it does, how to use it, and what options are available to use. It is one of the best resources to learn about a given command. The man command should be your first stop to learn about a new command.

To see the "man pages" for the cat command, you would run the following.

You would then be presented with text describing the cat command and its various options. To scroll down in the presented interface, press the "j" button on your keyboard, or use the down arrow key. To scroll up, press the "k" button or the up arrow key. To quit the man pages, press the "q" button (for quit).