Well, to make it a bit more accurate on the Nikkor nomenclature: basically their lineage works in this order:
There are basically two general types of Nikkor AF lenses; original screw drive lenses (AF) and later built-in motor drive lenses (AF-I/AF-S.)
1) AF = Autofocus lens (screw drive) - first AF lenses from Nikon.
2a) AF-I = Autofocus lens with an integrated coreless motor. These were the first Nikkors with integrated AF motors (1992) and were D-types (see 'D' below.)
2b) AF-S = Autofocus lens with built in 'silent wave' AF motor. Basically an update to the AF-I (1996.) These are newer designs and also include distance information to camera. They may or may not have aperture rings. (Two examples are the AF-S 17-35mm f/2.8 'ED' (w/ aperture ring) and the AF-S 17-55 f/2.8 G 'ED' 'DX.' (no aperture ring - G designation, see below.))
--------------------------------------------
Within the two basic types of AF lenses listed above, are several acronyms that can either be included in the lens name, or can be seen on the lens as gold letters; 'D', 'G', 'ED', 'N', 'DX', 'VR' and others. They can apply to various distinguishing characteristics of the lenses, such as 'distance' communication, aperture design, extra-low dispersion lens elements, etc...
'D' = AF lenses (screw drive or AF-I) with (D)istance information transmitted electronically to camera, works with 3-D metering, flash, etc. This is usually seen on older design lenses of the screw-drive type, although many are still currently available new. (AF Nikkor 80-200mm f/2.8 D is an example.)
'G' = AF lenses without aperture ring. These would be like Canon AF lenses, everything is electronic. All the newer lenses, kit and pro, are AF-S lenses with 'G' designation. 'G' lenses also transmit distance information electronically to the camera (replaced 'D' in newer lenses.)
'VR' = vibration reduction. Same thing as image stabilization.
'DX' = AF lenses designed for DX bodies (crop sensor.)
'ED' = extra-low dispersion lens elements in the lens.
'N' = nano coating on lens elements. This is newer.
There are other acronyms like 'IF' for internal focusing, 'RF' for rear element focusing, 'DC' for defocus control which may be seen on some specialty lenses. The designation 'FX' hasn't been actually used on lenses yet, but it has informally been used to describe lenses that will cover a full-frame (FX) sensor with their image circle. If it doesn't have a 'DX' on it, it's basically a non-labeled 'FX' lens. All original film (35mm) lenses are, of course, 'FX' if you use this informal designation for "full frame."
Yes, it's a bit confusing when you are confronted with all the variations, but it also can be understood once you know more about how the Nikon AF lenses developed over the years. Every lens tells a lot about it by its name and the designation labels on it.
BTW, for trivia's sake: older Nikkor manual lenses often had a letter which designated the number of lens elements in the lens, but that's no longer the case.