Veneers are thin, layered shells of porcelain or composite which can be attached to the teeth. They are used in situations when teeth are damaged, chipped, excessively stained or worn. They can also be used to alter the shapes of teeth and close gaps between teeth as required. Veneers if looked after well can last longer leaving a stunning long lasting smile they are not particularly invasive and often require minimal if any natural tooth adjustment at all.
Veneers enable a quick way and guaranteed way to whiten correct any minor discrepancies in tooth shape. Usually they are made of porcelain and are performed on 4-6 teeth so that the shade and shape of the new teeth are kept uniform. Minor orthodontic discrepancies can be camouflaged with porcelain veneers which could be of benefit particularly if you are not keen on having any orthodontic treatment.
The dentist providing the veneers will look at the current shape of the teeth, their colour, your facial and gum contours as well as things like lip position and tooth symmetry to make a decision on the character and profile of the veneers. However, the dental lab can perform a waxed version attached to a study model of your teeth so you can see and even trial the smile before any treatment begins.