potatoes

I can't believe this is real. They grafted tomato plants on potato rootstalks, and it works?! I can't get my mind around it. I know they are in the same plant group but... :duc

...but do they really taste that much different that one would get all these different varieties? Or do they just get those varieties so they can say they are growing all these varieties? Was visiting a UK garden site and they have more names for tater varieties over there than you can shake...