A dental veneer is a very thin layer of material used to cover only the front surface of the tooth / teeth in order to improve aesthetics. They are bonded to the existing teeth in order to change the appearance of colour, shape or size.
There are two main types of material used to fabricate a veneer: composite and dental porcelain. A composite veneer may be directly placed (built-up in the mouth), or indirectly fabricated by a dental technician in a dental lab, and later bonded to the tooth, typically using a resin cement such as Panavia. In contrast, a porcelain veneer may only be indirectly fabricated. Full veneer crown is described as “A restoration that covers all the coronal tooth surfaces (Mesial, Distal, Facial, Lingual and Occlusal)". Some content thanks to Wikipedia.