Grab a calculator! I'm going to teach you about a new button.
Look for it... It will either be
 |
or |  |
(It's probably above one of the other buttons.)
Find it?
It's called a factorial.
Here's an example:
(No, this isn't just an excited 5.)
Here's what it means:
Check it by multiplying it out the long way, then try the button.
Here are some others:
