Well, if you're eating it and it tastes sweet, you're eating what I call sweet corn. Sugar and butter corn must be a regional term???

I've never heard it called that before.
The company that sells us our field corn always gives us a some sweet corn to put out every year. We always plant a few acres, but not a whole lot. We just have it for our own use and to give some to friends and family. We don't even mess with trying to sell it because there are so many other people doing it that there just isn't much money in it to make it worthwhile unless you'd go large scale and produce a lot of sweet corn to sell to grocery stores, etc. And sweet corn just takes a lot of extra management and work.
My favorite variety is called Ambrosia and looks like this.