DX lenses vs FX lenses
Nikon lenses come in two main types, FX and DX. FX lenses are designed for fullframe cameras, while DX are designed for those with a smaller Aps-c-sized sensors.
You can use an FX lens on a DX camera, but the cropping effect boosts the effective focal length of the lens by a factor of 1.5x. This offers a bonus at telephoto lengths, with a 70mm focal length increasing to 105mm, but is a distinct disadvantage at wide-angle focal lengths, as a 24mm lens has an effective length of 36mm, which is hardly wide-angle at all.
Likewise, you can also use DX lenses on FX cameras, but the image area will be cropped to the central portion of the sensor, thus producing lower-resolution shots.
For this reason, DX lenses are usually designed to make up for this wide-angle shortfall. So a kit lens with an 18-55mm zoom range equates to a zoom range of about 27-77.5mm in full-frame equivalent terms – close to the 24-70mm of a more standard zoom.
However, there are some telephoto zoom DX lenses, such as the Nikon AF-S DX 55-200mm f/4-5.6 G ED VR II. Because they only need to project a smaller image area, they can be manufactured smaller and lighter than an FX equivalent lens.