A lens is simply a device for focussing the scene in front of you onto the cameras sensor. All cameras have lenses. Some are built in (as in compact cameras and prosumers) and some are detachable (as with SLR cameras). All of them do the same job.
There are different types of lenses. Standard lenses will cover most normal jobs portraits, simple landscapes and such like. However there are telephoto and wide angle lenses also.
Telephoto lenses basically bring far away things nearer. A wildebeest on the African plain is dangerous if you get too close, so a telephoto will get a closer image without you moving yourself.
Wide-angle lenses make you see a broader area of the scene in front of you. It will make the wildebeest look smaller and farther away but it will include a larger breadth of the scene and enable you to see the bigger picture.
Its sometimes hard to choose which lens to get but luckily there is a cunning way of making sure you have a lens for virtually every situation. Manufacturers now very kindly produce zoom lenses. These are lenses that are normal until you twist or push or pull parts of it then they become telephoto. Or, one moment they are wide-angle then they become normal again. We commonly refer to them as short zoom (going from wide-angle to normal) or long zoon (from normal to telephoto. Between them, you will hardly ever need another lens.
OK, you can get super zoom lenses and super wide-ange lenses, but these are for specialist use only or ar purchased by people with more money than sense. For most purposes you will feel entirely commfortable with a short and a long zoom. Talk to your local dealer and ask for a demonstration.
Eric Hartwell runs the photography resource site http://www.theshutter.co.uk and the associated discussion forums as well as the regular weblog at http://thephotographysite.blogspot.com
