Feynman diagrams were developed by Richard Feynman to graphically represent the fundamental processes of interactions between particles in quantum field theory.
A whole series of quantities and mathematical calculations on the behaviour of particles such as electrons, photons, quarks etc. are depicted in geometrical diagrams that are easy to manipulate.
In this way all these difficult calculations with obscure meanings are replaced by a simple combination of physical images given by the corresponding diagrams. The results of calculations made using these diagrams are not only obtained faster and more easily, but they are physically much easier to interpret.