Tau neutrinos are created by radioactive decay. They are much rarer than muon neutrinos.
When a tau neutrino interacts with an atom, it creates a new type of neutrino which is called a tau antineutrino and decays into an electron neutrino with a half-life of 1.3 picoseconds.
Electron Neutrino
An electron neutrino is created in nuclear fusion processes, like nuclear fission.
When an electron neutrino hits an atom, it changes into an electron antineutrino which decays into a positron antineutrino with a half-life of 0.7 microseconds.