When you're typing a lot in a terminal and want to clear the screen quickly, you can do so easily a couple different ways.
The one most people know about:
Code:
clear
Yeah, simply type 'clear'.
The one you'll use a lot more:
Code:
ctrl + l
(hit the ctrl key, then a lowercase L)
It doesn't make everything go away, you can actually see everything if you scroll up, but its very handy and I can't tell you how many times I use it each day.
(really - I can't tell you, because when you type 'clear' you'll see it in your history, but if you use ctrl-l, it doesn't make it into history)