Supervisor: Steen Hannestad

String theory is a famous part of theoretical high energy physics, but this fame only runs skin-deep. Most people interested in physics will likely have heard about string theory, perhaps even superstring theory and M-theory, but when asked, few would be able to say more than that it concerns tiny vibrating strings in a large number of extra dimensions.

In this talk, I will try to shed some light on what string theory actually is in a qualitative manner, as well as its pros and cons in the context of the generally accepted standard model of particle physics and its problems. I will present both string theory, superstring theory and M-theory, highlighting both similarities and differences between these theories. Among the related concepts I will mention are supersymmetry, gravity, duality and compactification.