Maybe I can help a bit.
Non AI, AI, and AIS are the designations for the older manual focus lenses used in older film cameras. Newer digital cameras can usually use these lenses, but through-the-lens metering and auto-focus won't be available.
The AI, AIS lenses may have exposure coupling rings which will hit the flash housing on newer Digital cameras. These projections can usually be removed.
E stands for better lens construction. Initially it really mattered, but as time went on, Nikon designated cheaper lenses with the E or ED logo as well.
D is the designation given to lenses which can adjust the shot settings based on feedback from exposure acquisition during focusing and shutter open time. It's not that important to getting good shots.
All lenses following here have the D capability.
G lenses (sometimes called gelded) have no aperture adjustment on the lens itself. Focus is adjusted by the camera electronics and either by the camera motor or in-lens motor. All G lenses have D function as well. These lenses are generally plastic and cheaper to manufacture. They can also be manually focused.
DX lenses are designed for DX cameras which have smaller sensors. When used on full frame professional type cameras such as the D3 or D700 which have large sensors, there will usually be vignetting.
AF-S lenses have the motor (S stands for silent) within the lens itself. Cameras such as the D40, D3000, D5000 which have no in-camera motor to drive focus are restricted to these lenses if the auto-focus function is desired. Typically labeled as AF-S ED G. The D40 and it's successors can use most any Nikon lens, but non AF-S lenses will need to be manually focused.
There is a benefit to this type of plastic in-motor lens and smaller non motorized body. Camera's such as the D40 are really light and easy to handle. I don't think there is much correlation between lens designations, price and the quality of the image. Some of the cheapest lenses are the sharpest and have the least distortion, flare, and color fringing.
It's best to read reviews such as from Ken Rockwell before buying a Nikon SLR lens. A similar lens costing 1/4 as much as the one that's highly priced and touted may actually perform better. One good thing is that most all Nikon lenses are excellent performers.
Hope this helps,
NORMB.
