The four fundamental forces of the universe are said to be the strong nuclear force, the electromagnetic force, the weak nuclear force and the gravitational force.
The gravitational force which acts over a relatively long distance is said to be the weakest while the strong nuclear force that acts over a shirt distance is said to be the strongest among them.
The strong nuclear force is present between protons and neutrons within the nucleus while the weak nuclear force is responsible for the radioactive decay in some elementary particles.
The electromagnetic force is the one that we find inside and between atoms while the gravitational force is the one that hold the universe together.
The electromagnetic force was derived by James Maxwell by combining the electrical and the magnetic forces. Though scientists have been trying the same thing with combination of the other forces no such force has yet come into being.