Custom-made porcelain veneers are placed on the front of teeth to disguise various imperfections for a natural and beautiful, healthy-looking smile.
They can serve for cosmetic and dental conditions, such as creating an aligned smile by bonding them onto crooked/misshaped teeth, onto discolored teeth, etc.
There are some situations in which veneers would be inappropriate. If you have significantly misaligned teeth or a large gap, orthodontics might be a more appropriate solution than veneers. And if you lost a tooth structure from decay or trauma(or a particularly severe grinding habit), it might be better to restore your teeth with porcelain crowns that cover the entire tooth.