A Feynman diagram is a graphical representation used in quantum field theory to visualize the interactions between particles. Named after physicist Richard Feynman, these diagrams depict the paths of particles as lines, with vertices representing interactions. They help simplify complex calculations in particle physics by illustrating how particles exchange forces. In a Feynman diagram, different types of lines represent different particles, such as fermions (solid lines) and bosons (dashed lines). The diagrams can show processes like particle collisions or decays, making it easier for physicists to understand and predict the outcomes of these interactions in experiments.