String theory helps human beings understand the nature of the universe and how it works. There are no practical applications for string theory, as of 2014.
String theory is made up of many different theories with diverse mathematical formulas. In theoretical physics, a string is described as a one-dimensional, microscopic filament of energy. A string, in combination with a brane, is the fundamental object in string theory.
String theory views all the fundamental particles in the universe as expressions of these strings. Physicists also study the configuration of these strings. One major goal in string theory is to determine how these configurations resemble the particles we observe in our universe.
By studying the mathematical theory known as string theory, scientists hope to explain certain phenomenon that is currently unexplainable using the standard model of quantum physics.