GB means giga byte or how much memory an xbox hardrive has
Arcade = no hardrive Pro = 60 gb hardrive Elite = 120 gb hardrive
Yes.
20 GB hardrive.
No.
about 120 to 250 GB
hardrive
The latest model: The 250GB hardrive
No, I play halo reach on my 4gb xbox.
Yes, you can use a 20 gb hard drive on the elite model.
That depends whether you have more than 4 GB's of data saved or plan on getting that much data.
It all depends on what your looking for .The elite is more money while it is a different color and comes with a 120 gb hardrive . While the arcs come with no hardrive and i believe cost around 150 USD dollars at walmart. I would suggest you buy a Xbox 360 slim it comes with 5 usb slots, 250 gb hardrive and a built in wifi receiver. ( so you don't have to buy a wireless receiver. That is if you are using wifi.
For a pro console of 60 GB hardrive, probably a good 249.99. Maybe cheaper depending which places you find.