I am currently taking photography classes, and have a LONG way to go! I own a DSLR and am in the process of forming my kit. At this time I'm looking at lenses. My manual says my camera will take most CPU lenses (Particularly D and G).

My question is the following. There is an X mount lens, that claims will fit my camera as well, except it will only work on Manual which is no big deal to me. Does that mean I NEED A TELECONVERTER? It doesn't say

And just how DO teleconverters work???

If the lens is designed to fit your camera's lens mount no adapter/converter will be required.

Teleconverters are designed to extend the focal tength of a lens when mounted between the camera body and the lens. For example a 1.4X converter will turn a 100mm lens into a 140mm lens and a 2X converter will stretch a 100mm lens to 200mm.
This extra length comes with a loss of light though, a 100mm F2.8 lens becomes a 200mm F5.6...nothing for free here.

There are also Adapters available to mount lenses to cameras with different lens mounts so you can for example mount a Nikon lens on a Canon body with the right adapter, most auto features are lost though.

I just changed over to a DSLR and auto focus lenses. I used to think auto focus was just fancy schmancy stuff I didn't need but the Auto Focus and Image Stabalized lens's I have now are amazing. I have gotten lots of excellent shots I would have missed with my old slow manual focus film burner. Unless you only ever plan to take pictures of rocks and trees I highly recommend spending the extra for the auto lenses.

Enjoy your new hobby. Steve P.

You will also lose some image quality. It varies between brands and lenses. Usually 1.4x converters will perform beter than 2x in terms of image quality.