Basic Commands 2. The most basic idea is that you type the name a command that you want the computer to perform. It typically provides some information about who or where you are, though it is configurable to display anything. If you think it's odd that the prompt tells you who you are, you must understand that Unix is a multi-user system, and you could be logged in as any number of users. Unix uses what's called a hierarchical filesystem.
Directories can hold files or other directories.
It gets easier with some examples of the basic commands. This would be a typical top-level directory structure for Linux. By default ls lists what is in the current directory. This is called passing an argument to the command. Commands can have different numbers of arguments which may or may not be optional.