Why is the conference called "Lepton Photon" ?

In other words, what is the connection between leptons and photons ?

Well it turns out that the photon interacts with charged leptons like the electron. To interact, implies the presence of a force, in this case the electromagnetic force. It means that an electron can emit or absorb a photon, or collide with one. It turns out that our current understanding of this interaction is very complete, even at the quantum level, and is extremely accurate in predicting a wide range of phenomenon.

This conference covers much more than just leptons and photons, but our understanding of leptons and photons and how they interact is a model for which the understanding of all the other forces is based on.