2.4.1 Leptons and Quarks
Matter is made up of leptons and hadrons. Leptons include, electrons, muons, taus, electron neutrinos, muon neutrinos, and tau neutrinos. Hadrons are made up of two categories, baryons and mesons. Baryons have 3 quarks, all quarks or anti-quarks, mesons are made up of two quarks, one quark and one anti-quark.
Note, that for every particle, there is an anti-particle of equal mass, but opposite charge (and baryon number and strangeness). Antimatter and matter annihilate when put in contact, which makes antimatter hard to store and produce because it cannot be stored in matter or it will annihilate.
2.4.2 The Four Interactions
There are only four real forces or interactions (all the rest are simply types of the these four):
