Getting help

All but the most minimal environments tend to come with manual pages (manpages), which are documentation that you can use to learn (or remember) how to use the command-line programs you have available to you.

Use man $COMMANDNAME to get information on a command. For example, man ls will print something like this:

LS(1)                                                    General Commands Manual                                                   LS(1)
NAME
     ls – list directory contents
SYNOPSIS
     ls [-@ABCFGHILOPRSTUWabcdefghiklmnopqrstuvwxy1%,] [--color=when] [-D format] [file ...]
DESCRIPTION
     For each operand that names a file of a type other than directory, ls displays its name as well as any requested, associated
     information.  For each operand that names a file of type directory, ls displays the names of files contained within that directory,
     as well as any requested, associated information.
     If no operands are given, the contents...