I read a bit about string theory but i don't really get the idea. Can someone explain it to me clearly, perhaps in a way that i can visualize it?

Szabo's lectures on string theory may be useful to you. Pay attention to the introduction and the section on the classical (bosonic) string.

string theory basically says that the 3 constituents of elementary particles, such as protons - the quarks - are instead actually tiny vibrating strings. These strings are exceptionally small. billions and billions of times smaller than the proton itself. so small its beyond anything we are currently capable of to be able to see them, so thats where the theory gets a little scepticism. So just visualise the nucleus of an atom, then the protons etc and then instead of imagining quarks (or point particles), just think of them as tiny little vibrating strings..

 

its really just planck scale rubber bands in a way..