Here's a breakdown:

* Photo: Refers to light, as this process is driven by light energy captured by chlorophyll.

* Phosphorylation: Refers to the addition of a phosphate group to a molecule, in this case, ADP (adenosine diphosphate) to form ATP (adenosine triphosphate).

How it works:

1. Light-dependent reactions: Light energy is absorbed by chlorophyll and used to excite electrons, creating a flow of electrons through an electron transport chain.

2. Proton gradient: The energy from the electron flow is used to pump protons (H+) across a membrane, creating a concentration gradient.

3. ATP synthase: The movement of protons down their concentration gradient through the enzyme ATP synthase drives the phosphorylation of ADP to form ATP.

So, photophosphorylation is the key process that generates ATP, the energy currency of cells, during photosynthesis.