I don't think any theory proposed by physics will ever offer a purpose, only how.

And superstring theory doesn't have anything to do with magnetism, gravity or any other law of attraction. I was just saying that gravity, in a way, is electromagnetism.

All string theory does is attempt to make sense of the fact that even though both quantum mechanics and general relativity make sense on their own, they cannot coexist without something bridging the gap. Hence the apparent discovery of strings and extra spatial dimensions.

It's really fascinating stuff. I recommend "The Elegant Universe" by Brian Greene if you really want to delve into it.

One really cool thing I learned is about the origin of the universe, that at the moment right before "the big bang," all of the universe, everything in existence, compacted into a tiny mass, about one billionth of a trillionth (if I remember correctly) the size of an atom and then just exploded to create everything we know today.