If it's the under-shield it's probably better to get an aftermarket part instead of a Toyota part as they will sting you with the price. Try to avoid plastic if you can and use sturdy screws instead of those crappy plastic ones.
Et means offset I believe and it's the mm distance between the centre line of the rim, and the line through the hub. You need to get it right else your wheels may scrub.
I just noticed this vid floating around on some social sites and thought it mite be worth posting for a giggle. This drummer is clearly superior to his band-mates and doesn't mind showing it.