A camera lens is one of the most important part of the camera, much like our eyes. Without it the camera will not be able to view the scene around and focus on anything.
When buying a camera with fixed lenses, it is important to understand the characteristics of its lens in order to fully asses whether it is the right one for your style of photography. For DSLR or bridge cameras with interchangeable lenses, this doesn't pose much of a problem since you will just have to replace the lens with something more appropriate. You still need to understand the properties of the lens you are going buy otherwise you will be persuaded by a sales person to flashy specs that you don't actually need.
If you're a beginner and doesn't really know what type of photos you will be taking, it would be advisable to start off with a lens that has a practical range on both wide angle and telephoto. Most cameras offer a very good starting zoom range of 24-105mm. This is a good all-around range as it covers a good wide angle of 24mm up to a decent telephoto of 105mm. This range would be about what you will need for typical family events, trips, group photos, and portraits. DSLRs usually offer a starter kit lens 18-55mm for APS-C cameras (equivalent to about 28-85mm) or 24-105mm for full-frame cameras, which has a good focal length coverage for typical everyday activities.
For photographers who already know the focal range they need and the specific type of photography they want, it is equally important to know all other properties of a lens such as aperture, image stabilization, auto-focus, focusing speed, minimum focus distance, bokeh, corrective coatings, etc. These properties will help to improve the hit rate and enhance the quality of the photos and give the photographer more creative options.