Physic is always a subject of imagination and equations. Everything should be proved experimetally as well as theoratically otherwise it is same as nothing but paper work only.
General we study four different fundamental forces in nature in physics and now a days some scientists try to introduce a fifth force though its only theoretical and yet not observed. There is also other theories like Grand Unified Theory(GUT) which combine all those forces into a single force but only at high energy (I.e. at high temperature ) only.
Above diagram shows at what temperature these forces merged together to form a single force or onterainter. Well are u thinking why is it?
Generally we study these forces by studing there fields But quantum physics describe force in the form of exchange of certain elementary particles called bosons in Quantum Field Theory(QFT). Bosons carry the force, so they called as force carriers. So in this theory every force has a its carrier boson partical.
Now we are going to see brief introduction to all those 4 forces.
1]ELECTROMAGNETIC FORCE
This force only acted on charged particles and is second strongest, mostly aplicable force in the field of electronics.This force is main cause of our existance as a living being, because it holds nucleus and electrons together in first place to form an atom which is basis for further complex structures. Electricity is also contribution of this force with help of charged particles.
2]STRONG FORCE
This is the world's strongest force, but acts on a very small range comparable to radiou of a nucleus of a atom. Because it holds protons together in a nucleus. Strong force dominates over electromagnetic force (which try to repel protons) and holds protons together. This is a short range force and hence we are not able to experience its full strength in our day to day life.
But though we study it's residual as wander wall force which holds atom and/or molecules together. following figure shows graph of potential energy due to strong force vs distance.
3]WEAK NUCEAR FORCE
Weak force is not really that weak as its name suggests. This force causes the nuclear decay in the particles. So weak nuclear force plays vital role in fission process because it a type of nuclear decay.
4]GRAVITATION FORCE
And at last most popular and yet world's most weak force. Though it is weak it is dominated force in the world. Large scale objects or systems generally interact with this force. As strong n weak forces are short range forces and electromagnetic force cancel out at large distances only gravitational force is seems to be active.
Though einstein says it is not a force but only a curvature in space-time due to large energy density.