In theoretical physics, M-theory is an ultimate theory that mathematically combines the five superstring theories and the supergravity theory in eleven dimensions, as well as the four fundamental interactions.

This is the most accurate summary that I have found about string theory:

(via xkcd)

So, obviously I can not. For those who don’t have access to the universal doubts *fixers* (Wikipedia, Google, or your Mom) a friend of mine suggested *The Elegant Universe* by Brian Greene.