What is the role of the thylakoids in the process of photosynthesis?

Chlorophyll is found in the thylakoids themselves, but the light reactions happen at the thylakoid membrane.

The aforementioned reactions encompass light-induced water oxidation and oxygen evolution, proton pumping through thylakoid membranes in conjunction with the photosystems and cytochrome complex electron transport chain, and ATP synthesis via ATP synthatase, which leverages the generated proton gradient.

The chemiosmotic potential is established by the carriers of the electron transport chain using some of the electron's energy to actively transport protons from the stroma to the lumen; during photosynthesis, the lumen becomes acidic, representing a 10,000 fold concentration gradient for protons across the thylakoid membrane. This is one of the main functions of the thylakoid membrane and its integrated photosystems.

The membrane-bound thylakoids, which house chlorophyll and other pigments that absorb light energy and transform it into chemical energy in the form of ATP and NADPH, which power the synthesis of organic molecules during the light-independent reactions (Calvin cycle) of photosynthesis, are the areas within chloroplasts where the light-dependent reactions of photosynthesis take place.