What is Photosystem 1 and Photosystem 2 in simple terms?

Photosystem two- PSII
Chlorophyll a absorbs P680nm.
The P II system passes electrons through ET chain of acceptors that generate  NADPH
To replace the e- P II splits water, making oxygen- photolysis 2H20 -> 4 H+ + O2 + 4e-
The H+ proton gradient => ATP
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/L/LightReactions.html
While the electron is still in a partially excited state it is passed to PS I (where it is re-energized by another photon from the antenna array).

The electron from PS II is lost and is only replenished through the oxidation of water. There is a flow of  the H+  from lysed water that goes to the stroma along with the O2 as waste. ? noncyclic


Photosystem I (PSI) has chlorophyll a with no or few chlorophyll b and can accept a photon from the antenna directly and an electron from PS II.
The combined energy from a fresh photon excites the old electron from PS II. Then the electron is  channeled down the electron transport chain generating  ATP.  The electron cycles back to reaction center's chlorophyll a
PSI Chlorophyll a (P700) absorbs light of 700 nm maximally. PSI is cyclic and uses longer wavelength light.

http://www2.mcdaniel.edu/Biology/botf99/photo/l4ightrx.html
http://staff.jccc.net/PDECELL/photosyn/lightreact.html

They are just locations on the plant cell membrane where the chlorophyll are located.