What kind of lens do I need?

Lens quality also has an important influence on the image quality - there is little point in having a high-resolution digital conversion of an unsharp optical image. Lens quality can only really be assessed by practical tests, but the better-known camera and lens makers - Nikon, Nikon, Olympus, Konica Minolta, Pentax, Leitz as well as Sigma, Tamron, Tokina and others - can generally be relied on to produce good quality. Fixed focal length lenses
These lenses offer no optical zoom. Look for autofocus instead of fixed focus, as well as selectable macro and landscape focus modes.
Retractable zoom lenses
These zoom lenses retract into the camera body when the camera is off and extend when it's on.
Interchangeable lenses
Digital SLRs use interchangeable lens systems, which means that you can detach the entire lens from the camera body and replace it with any other compatible lens.
What a Zoom Lens Can Do For You?
Most people think of a zoom lens as a tool for getting closer to your subject. It is. However, it can be used for so much more. The real benefit of using a zoom lens is the speed and ease with which you can recompose your picture.
What a Fixed Lens Can Do For You?
Fixed-focal length lenses will give, in theory at least, the sharpest results. This makes sense; if you want the least distortion, etc., you want to have the least amount of glass between you and your subject. A zoom lenses usually consists of a great number of different elements while a fixed will have few.