Neutrinos and the Standard Model
The Standard Model of particle physics is based on the idea that there are three distinct kinds of sub-atomic particles: (1) fundamental fermions like quarks, electrons, and neutrinos, (2) gauge bosons like the photons, gluons, W, and Z particles that are responsible for forces between particles, and (3) a complex scaler particle like the Higgs that interacts with particles to give them mass. The particles form a sort of "periodic table" similar to the chemical elements, as shown here. The fundamental fermions are classified as quarks (purple) or leptons (green) depending on whether or not they interact with gluons (g) via the Strong Force. The quarks do interact with gluons, and therefore make up the protons and neutrons that are inside atomic nuclei. The leptons (like the electron) only interact electrically via the photon (γ) or weakly via the Z or W. This is why electrons are outside the nucleus to make the atoms of the matter we are familiar with – they just don't interact strongly enough to keep them penned up!
Neutrinos (ν) have no electric charge and thus only interact weekly with other particles. So weakly, in fact, that neutrinos from the sun pass right through the earth and allow specially designed neutrino detectors to image the sun when it is below the horizon!
Like the quarks, neutrinos come in three types called flavors. For neutrinos, the names of the flavors are e μ and τ based on the association of the flavor with one of the charged leptons: electron (e), muon (μ), and tauon (τ).
Neutrino Oscillations and CP Violation
Are Neutrinos Fundamentally Different?