Where can you find instructions on this thing?

On a Linux box there are three places you can find more information about a command-line application:

• The Help page: Almost all Unix and Linux applications have a help file that you can access by typing the application name and -h on the command line, for example, root@kali-01: ~# nmap -h.

• The Man page: Here is a full manual for most modern command-line applications that you can access by typing man and the application name on the command line. For example, root@kali-01: ~# man rsync gets you a pretty good explanation of how to use Rsync, the secure and logged file transfer protocol. Man pages are of varying quality and many of them are actually written by rocket scientists, so a newbie may have to research how to read the manual page before it can be useful. The Nmap man page is clearly written with understandable examples to try out.

• Info pages: For BASH shell built-ins, there is a group of info pages instead of man pages. To get at the info...