http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html
Photons are electromagnetic radiation with zero mass,zero charge, and a velocity that is always the speed of light.
http://photontheory.com/pte.html
Light is defined as a transferring media of energy through space.
http://www.artinaid.com/2013/04/what-is-light-or-electromagnetism/
Richard Fynman good talk on Light and Quantum https://www.youtube.com/watch?v=eLQ2atfqk2c&app=desktop
http://www.s-cool.co.uk/a-level/physics/particle-classification-and-interactions/revise-it/fundamental-forces-and-exchange-p
Virtual particle - good explanation
The Tiny Timescales of the Quantum World
Albert Einstein already explained the "photoelectric effect" in 1905: light transfers energy to an electron, removing it from the metal. This happens so fast that for a long time it seemed impossible to study the time evolution of this process. In recent years, however, attosecond physics has advanced dramatically, so that time resolved analysis of this process has become possible.
An attosecond is a billionth of a billionth of a second (10^-18 seconds). This is approximately the time it takes light to travel the distance from one atom to the next. Using ultrashort laser pulses, time can now be measured with a precision in the attosecond range.
Relativity of colors https://www.youtube.com/watch?v=PJBOahK73Og