A pion is a type of subatomic particle that plays a crucial role in the strong nuclear force, which holds atomic nuclei together. Pions come in three varieties: positively charged, negatively charged, and neutral. They are classified as mesons, which are particles made up of a quark and an antiquark. Pions are produced in high-energy processes, such as those occurring in particle accelerators or cosmic ray interactions. They have a short lifespan, decaying into other particles, including muons and neutrinos. Understanding pions helps physicists study the fundamental forces and interactions that govern the behavior of matter in the universe.