What is the difference between different kinds of camera lenses? 18-55, 55-200, etc. etc..?

I'm shopping for a camera, and I have to buy the lens separately (the d50, to be exact). How do I figure out what the different lenses are? I know it has something to do with the distance between mirrors and lens, or something like that, but what is the effect that each kind has on the picture? What does it mean?

Lower numbers mean a wider angle of view and usually more light gathering power. Higher numbers are more telephoto and usually require more light. It is difficult to hand-hold lenses over 200. The normal lens that comes with a 35mm camera is about 55. an 18-55 lens would go from wide angle to normal and a 55-200 would go from normal to telephoto and is much larger and heavier.

A 50 mm lens will give you an image on the film or printed photo that is the same size as the image your eye sees. Any lens that has a range is a zoom lens. A lens that goes from, say 18 to 55 mm, goes from a slight magnification or close-up (55) to a wide-angle or smaller image taking in more of the scene (18). The higher the number, the closer-up the image is, and the worse the picture looks due to the magnification of even slight motion.

Lens are based on angle of view. A "normal" lens is very basically what you would see with your eye without the camera. For the D50 & other digtal cameras this is arounf 35mm - 40mm. Any numbers less than that are considered wide angle with the smaller the number the wider the angle of view. Any thing more than those numbers is telephoto which increases the "magification" or gets you closer to the subject. Again, the higher the numer the closer you get

Asking a question like this...are u sure you are ready for a DSLR? :)

On a more constructive note, go to www.dpreview.com and check out their forums. Plenty of info there. Also I would suggest picking up a basic photography book to get the fundametals (Barbara London's & John Upton's Photography is a great start). Otherwise, you will simply not enjoy the camera. "My point-and-shoot takes better pictures" you will say. Good luck and have fun.