Veneers are used when a front tooth is discoloured.
A thin layer of enamel is shaved off the tooth and a cover like a false finger nail is glued on. These veneers are designed to be the same colour/shade as the teeth either side and are generally made off site in a dental lab.
Although they can look nice, think carefully before you decide to have a tooth shaved down for only aesthetic reasons, remember enamel does not ever grow back.
Discussing options with your dentist is a good idea.