That's okay. No one can.
Basically to make an absurdly complex theory absurdly simple, the gist of string theory is that... well.
Imagine you have a guitar or violin or other stringed musical instrument. You know how the way you pluck/twang/whatever the strings makes them make different sounds? String theory is sort of like that. The basic gist is that the universe is ultimately and really made up of one-dimensional cosmic strings and that the various particles we observe are just the strings vibrating at different frequencies, kind of like how the same string on a guitar can make different sounds.