Simply put, string theory is an approach to modeling the four fundamental interactions of physics and resolving the conflict that they cause between classical and quantum physics. The four interactions that string theory models include gravitation, electromagnetism, strong nuclear force and weak nuclear force.
In addition to the four fundamental interactions, string theory utilizes five basic ideas to form its foundation. These include the ideas of strings and membranes of energy, quantum gravity, unification of forces, supersymmetry and extra dimensions. In particular, the strings and membranes claim has generated controversy, because it is purportedly impossible to produce supporting observational data.