A quick note about commands and arguments. A lot of programs use a similar syntax when it comes to passing arguments (or options) to a command. Not all do, but it's a good chance they do.
If there is a short command, the argument generally begins with one dash:
$ ls -a
If there is a long command that does something similar, it generally begins with two dashes, followed by a word:
$ ls --all
There are exceptions to these, but this is mostly true.