In a "theory of everything," one theory would explain the four forces of the universe: strong and weak nuclear forces, and:

Albert Einstein made many great contributions to science that include the Special Theory of Relativity and the General Theory of Relativity. But one of his theories -- the "theory of everything" -- was never completed. Einstein hoped that this equation, also called a "unified theory," would explain how everything in the Universe works. That's why we call it the theory of everything.
In a "theory of everything," one theory would explain the four forces of the universe: strong and weak nuclear forces, and:
gravity and electromagnetic force
energy and the forces of nature
good and evil
Gravity is the fourth force of the universe that would be described by a theory of everything. Although Einsteins general relativity theory describes gravity, it does not explain the other three forces.
One of the components of the theory of everything describes how the Universe works on a macroscopic level. This is called:
the General Theory of Relativity
the quantum theory
the itsy bitsy theory
The General Theory of Relativity describes how things work on a larger scale. The quantum theory describes how the Universe works on the atomic or microscopic level. Things at the atomic level are impossible to see with the naked eye.
At present, the closest scientists have come to a theory of everything is the "silly string theory."
The "superstring theory" describes a world in which all particles are like multidimensional vibrating strings; more specifically, particles are like notes on a musical scale.
theory of everything
What it is: a simple, yet complete, theory that explains how everything in the Universe works
First introduced by: Albert Einstein
Also called: unified theory
What it would encompass: theories of the physical world on the largest level and on the most microscopic level
Current models: string theories, super symmetry, and membrane theory