Electromagnetic Interaction 

Lepton Annihilation  

    Lepton annihilation is a process of where a lepton and it anti-lepton interact, such as a electron and a anti-electron (called a positron).  In the process of the interaction the both the lepton and the anti-lepton are "destroyed" releasing all of its energy in the form of photons.  The amount of energy released in the interaction is equal to E=MC^2.  The leptons aren't destroyed in the interaction instead 

Incoming lepton (on the top) and a Anti-lepton (on the bottom) interact and are "destroyed" in the reaction.  The "matter" of both particles are converted in to photons.  

The photons then "condense" and a lepton and anti-lepton are formed some time and distance later.   

    Before the Feynman Vertices both the lepton and anti-lepton are both real particles.  At the vertices the lepton and anti-leptons are annihilated, converting its real matter into light, the particles are now virtual, which means they simple don't interact with any real particles.  The photons then condense producing a lepton anti-lepton pair.  It is important to note that that in this interaction, the "rematerializes" lepton anti-lepton pair does not have to be the same type of particle (ei.  electrons and positrons) as the initial pair of particles.