Confusing letters and abbreviations, what do they mean?

~~ Nikon 50mm f1.8D AF Nikkor lens ~~ VS ~~ Nikon 50mm f1.8G AF-S Nikkor lens ~~

What is the difference between these two lenses? I know the AF stands for autofocus. But what on earth does nikkor mean? And what is the difference between the "D" and the "G" after the aperture… Also what's the additional "S" for?

Nikon: Brand (obviously)
Nikkor: Nikon's lenses. For lenses, I use nikkor/nikon interchangeably
50mm: focal length of lens
D: Has aperture ring
G: does not have aperture ring
AF: autofocus (camera body needs autofocus motor to have autofocus)
AF-S: autofocus AND the lens has the autofocus built in, therefore the camera body does not need an autofocus motor to autofocus

D lenses are older lenses and are almost always AF
G lenses are newer lenses and are almost always AF-S

if you want autofocus on entry level cameras, you must use G lenses.
if you want autofocus on anything above entry level, you can use either D or G lenses without a problem