In the natural world theoretical physics uses math and basic physics to interpret and explain information and attempt to rationalize phenomena. Albert Einstein used predictions based on calculations, and those calculations were based on math and theory. He was able to prove many natural occuring events that no one could see becouse the theory and ideas behind his predictions were sound. A physics theory involves one or more relationships between various measurable quantities. String theory is based on this concept and today has taken on a certain cachet among scientists. Its ideas are elegant interpretations of unseen forces and I will attempt to simplify them for you.
String theory consists of many ideas with various mathematical formulas. A manner to describe known natural forces (electromagnetic, gravitational,etc.) and matter in a math controlled system. Some critics have poo-pooed string theory because it has not proved experimentally testable ideas. Proving the theory would be expensive,engineering on a universal scale would be needed.
Because of the math involved, and the vast numbers these theories produce, scientists are fascinated by the idea and the new possibilities. String theory suggests that space/time has 11 dimensions,not the usual 3 space and 1 time,and can show universes with 4 observable space/time dimensions as well. String theories involve objects more than strings, or branes. The word brane, derived from "membrane", point to a variety of connected objects, such as D-branes, black p-branes and Neveu-Schwarz 5-branes. All believed to be related to each other. For example, the black hole-like black p-branes are identified with D-branes, upon which strings end, through Gauge-gravity relation. Experiments on this has led to new ideas on quantum chromo-dynamics, the basic ideas behind the strong nuclear force.
The idea behind string theory is the holographic principle, which states that the description of the movement of the surface of a black hole will describe the space/time surrounding it. Holography requires that a low-dimensional theory describing the fluctuations of a horizon will end up describing everything that can fall through, which can be anything at all. So the idea of a black hole horizon is a theory of everything.
The classic General Relativity Theory which you no doubt learned a little about in high school science, deals with Gravity in a space-time context. Gravity would bend spacetime and show velocity, speed of an object. Mathematically these ideas have been explored by Newton and Einstein. Picture a bowling ball on a waterbed. It sinks down and comes to rest. The Mass represents the bowling ball while the surface of the waterbed is our Space-time. This is gravity in action. Now, lets imagine this done on a graph or grid and follow the bowling ball with a line. It would show a curve as it sinks. That curve would represent acceleration, which is expected in a gravitational field. Space and time are relative. They affect each other.
Quantom Mechanics deals with matter on a much smaller level. All the way down to the particle. On a microscopic scale quantifying or measuring is difficult as the movement at that level increases causing velocity to increase. How can we measure space time outcomes using both principles?
Since Quantom physics has no way to bring gravity into its equations this is vexing. Relativity measures masses at known locations with known speeds giving us a mathematical equation. The two theories are contradicting. Relativity means that with no matter present space-time is a flat grid like our waterbed without the bowling ball. Quantom theory, drilling down to the particle level shows vibration, erratic and unpredictable as we try to measure a particle moving around.
String Theory ties the two together by showing particles as moving lines of energy(strings)instead of points or dots. These strings vibrate like a harp that is plucked. The amount of vibration would determine the amount of energy and properties of the particle. By combining both theories we can now use one value,the vibration of our "string". The theory of "Everything"!
Until now we believed in a 4 dimensional universe. String theory proposes a ten dimensional sub-space. This would inevitably challenge the rules and understanding of space and time itself. Perhaps other life forms in other galaxies have already mastered this understanding. Maybe someday the mechanics of it can be harnessed and manipulated. The possibilities are truly infinite.