Both photosystems have multi-protein complexes with pigments, and an electron transport chain, in their thylakoid membranes reaction centers that harvest energy from light photons and used for photosynthesis.
The difference is that Photosystem II has a quinone-type reaction center
while that of photosystem I have an iron-sulfur (Fe-S)-type. Additionally, in the electron chain reaction, photosystem I pass the electron to ferredoxin, while Photosystem II contains plastoquinone, which passes the energetic electron to cytochromes b6 and f.