Now that you've invested in a DSLR camera, what lens should you buy? First, you need to understand focal length, the most important lens specification.
A wide-angle lens refers to a lens whose focal length is substantially smaller than the focal length of a normal lens for a given film plane. This type of lens allows more of the scene to be included in the photograph, which is useful in architectural, interior and landscape photography where the photographer may not be able to move farther from the scene to photograph it.
Many lenses now come with built-in optical image stabilization (sometimes referred to as vibration reduction), that moves the lens elements in an attempt to counteract any sensed motion of the camera. This results in fewer blurred photos and is especially useful when you are zooming in low light or shooting with slower shutter speeds.
Fisheye lenses offer a full 180-degree viewing angle, but the image is distorted so the center looks like it's closer to you and the edges look like they're receding. It's a fun, distinctive effect, useful when trying to capture a wide, nearby scene. However, a fisheye lens will probably not become your standard-use lens.
f/2.8 or Wider Aperture
Aperture is the opening in your camera lens that determines the amount of light that passes through to the sensor. By using a lens with an f/2.8 or wider aperture, you can fade the background and focus on your subject in the foreground. You'll get a much more dramatic shot as your subject will "pop" from the photo. The result is a more desirable image with less "depth of field," or a more diffused background.