What is the string theory?

In my opinion, the string theory is one of the most beautiful to emerge in recent decades, although it still needs to become more than just a theory. 
We all know the world as we see it is made of atoms, made of electrons, protons and neutrons. Electrons are fundamental particles, while protons and neutrons are made of quarks.
We also know about the four fundamental forces: gravity, electromagnetism and the weak and strong nuclear forces. This is the Standard Model.
The String Theory is a bit more profound than the Standard Model and its purpose is to unify the structure of the Universe.

According to this theory, the electron is in fact a string in a loop. The oscillation of a string in a certain direction may create an electron, a different oscillation of a string would create a quark or a photon. Basically everything surrounding us is made of strings up to a super-microscopic level. The various manifestations of this strings define matter, the world and the entire Universe. The string theory is yet to be experimentally proven, but if it will, it won’t annul the Standard Model, but perfect it. – Roman Alexander

(The question was originally asked by Hriday Sharma)