What's the difference with motherboards?

I'm confused with the array of motherboards available.
What's the difference between a =A320 one and a =A3100+ one?
OK... I'd expect the more expensive one to have better capabilites.

But the thing is... there seem to be a million different motherboards
priced from =A340 - =A360: what's the big difference in these models.

OK... I do know a bit... like some motherboards are for Intel, while
others are for AMD??

BUT... even then... there seems to be a plethora of options available!

How do I choose?
What should I look out for?

Is a =A3100+ motherboard ever worth buying?
(Heck... I might as well buy a dual processor one for a bit more!)

I know about SATA - but even still, I'm confused about the number of
options available!!
Are there other things that are relevant?

Am I right in saying that the cheaper motherboards come with onboard
VGA and the more expensive ones don't?

AND... what makes should I go for when buying?
AND... which should I avoid!?

Any enlightenments would be helpful.

Thanks.


OM