More about leptons

Leptons (shown in green, above) are small particles that form matter, together with quarks. However, an important difference is that, unlike quarks, leptons are not bound by the strong nuclear (or "colour") force.  So leptons are free to move around through space, unlike quarks.

Leptons include the electron, muon and tau (as well as their neutrino equivalents of these 3 "generations" of leptons). 

Leptons like quarks, each have a spin of a half.  So, like quarks, they are a class of fermions (particles that have a spin of a half, or of an integer plus a half). 

Leptons have a charge of -1 (electron/muon/tau) or zero (neutrinos), whereas quarks have charges of either two thirds or minus a third.