What does "chlorophyll photosynthesis peak" mean in relation to photon wavelength?
First thing to note is that the absorption spectrum of chlorophyll A and chlorophyll B is similar but not the same. The reason for the appearance of absorption spectra is because the light is composed of photons of light.  Different photon has different  oscillation frequency and energy. The essence of Chlorophyll absorption is absorbing photons. After chlorophyll absorption of a photon, the electron transition from the ground state to the excited state, and get water electronic from the water cause decomposition. Only phonton that has resonant vibration frequency with electrons, and can meet the energy requirements of electronic transitions in order to be absorbed by chlorophyll. The Photon energy of different wavelengths of light is different. This is also the reason of different wavelengths of light affect chlorophyll light absorption.

Simply explain the absorption spectrum:  


280 ~ 315nm  has small effect of plant morphology and physiological processes
315 ~ 400nnm absorption rate is small, impact the photoperiod, prevent stem elongation
400 ~ 520nm (blue) Absorption ratio of of chlorophyll and carotenoid in this light is maximum, it has the greatest impact on photosynthesis
520 ~ 610nm absorption rate is not high
610 ~ 720nm (red) low absorption rate.  It has a significant effect on photosynthesis and light cycle effect of  chlorophyll.
720 ~ 1000nm Low absorption rate, stimulate cell elongation, impact of flowering and seed germination
1000nm converted into heat


p.s. white light is a mixture of light