Explain the process of annihilation?

Matter and antimatter will annihilate if they meet:
1) Particle meets antiparticle.
2) Both have rest energies due to their masses.
3) Both have kinetic energies due to their movement (if they are moving).
4) They annihilate to produce 2 photons which move in opposite directions.
5) Each photon energy = ½ the total (rest energy + kinetic energy).