In Games

How is it that they are able to fit a ton of games onto one cart? I figure it's new technology you get more memory, but how is it that the old NES can read it? Also, are multi-cart games usually lower quality IE: sound, graphics, color etc...

Multicarts are usually just sprite hacks of other games all crammed into one cart, so graphically they're very similar.

they can fit so many on there because the memory used by the NES carts is now Super Cheap, and there was no hardware limitation on storage with the NES, so it'll have no problems reading them.