Question Need help h1,h7,h11 lights

[SANCHOJG]

Hi i am new on this. I liked to know if any body can tell me the differencce on h1,h7,h11 lights thank you.

[velocitymotorsports]

H1 - Mostly used on projection bulb or fog lights
H7 - this is a single filament bulb used mostly for low beams on some vehicles.
H11 - same as the H7 but with a different base that installs into the back of the headlight housing.