AP Express vs. AP Extreme

I am completely green when it comes to wireless networking.

Can someone please explain the difference between the Airport Express w/ iTunes and the Airport Extreme Base Station?

Do they both do the same thing?

Bascially, yes:

With both you can connect them to a cable/dsl modem and share the connection wirelessly with other computers.
You can also plug in a printer and print wirelessly to that.

The extreme has support for more clients (50, has an extra ethernet port and has a built-in analog modem, in case you want to share an analog connection. There is also a version that can take it's power directly through the ethernet connection, saving you a power-wire. You can hook up additional antenna's to it as well.

The express supports up to 10 clients & has music streaming and wireless printing. It can be used to extend the signal of an existing airport extreme station.

The express is find for home use though..