...............would take too long to explain sb..............just Google ............but enter light bulbs..............or you're likely to get daffodils................ :o)
GZ10 is for spotlighting or decorative use, the GU is warmer sort of light and i think the par 16 is spotlight and the par 20 is floodlight, therefore giving wider beam, thats if I am remembering correctly, maybe somebody can explain better.
PAR stands for Parabolic Aluminized Reflector and these are used in recessed and track lighting. The numbers represent the diameter of the bulb (in 1/8ths of a inch), so the PAR 16 is 2" in diameter and the PAR 20 is 2.5" diameter.