Modern metal-free dentistry has evolved to be much more conservative in terms of tooth preparation.
A veneer is essentially a "conservative crown". Rather than encompassing the entire tooth, a cosmetic veneer, essentially covers the visible part of a tooth, preserving a large amount of the natural tooth structure.
Veneers can straighten, lengthen and whiten teeth, providing the desired smile and bite. Each veneered tooth must be shaped. This means that an outer layer of the natural tooth is removed to allow space for veneer placement.