The tau neutrino is a type of elementary particle that belongs to the family of neutrinos. It is associated with the tau lepton, which is a heavier cousin of the more familiar electron and muon. Neutrinos are neutral particles that interact very weakly with matter, making them difficult to detect. Discovered in the late 20th century, the tau neutrino is one of three known neutrino types, the others being the electron neutrino and the muon neutrino. These particles play a crucial role in the processes of particle physics and are important for understanding the fundamental forces of the universe.