First, let's make it clear that string theory is not completed yet and it may take decades or even centuries before it is. It has not been proven experimentally, though circumstantial evidence may surface in the next decade. It does account for seemingly random things like why there are the number of fundamental particles that there are. According to string theory, there are that many because it had to be that way. String theory has also solved a puzzle called the Bekenstein-Hawking entropy concerning black holes that plagued physicists for 25 years. The problem with string theory is that there are no exact equations yet, only approximations, and only approximate answers to the approximate equations.

The basic idea behind string theory is that the vibrational pattern of the loops determines the properties of a particle, such as its charges (electric, weak, and strong charge) and mass. In other words, the properties are dependent on the "notes" the strings play. The loops each have a whole number of peaks and troughs, as in the diagram. The more peaks and troughs there are, the more energy the string carries since it is moving more rapidly. Special relativity says that mass and energy are interchangeable, so the greater the energy, the greater the mass. The mass of a string also determines its gravity. In a similar way, the way a string vibrates determines its charges in the other three forces, but the reasons behind this are more complex. If string theory is right, instead of particles like electrons and quarks being made from fundamentally different material carrying the particle's properties, they are all made from the same fabric - strings.

There are several weak spots in the standard model that string theory fills. The standard model does not contain gravity. It also gives no reasons behind why there are the number of fundamental particles there are or why they have the properties they do. In fact, the standard model requires the input of these properties' values to work. On the other hand, string theory requires only one number for input - a value to set the scale of corresponding tensions between loops of strings.