According to Wikipedia, "dental braces (also known as orthodontic braces or tooth braces) are a fixed appliance used in orthodontics to correct alignment of teeth and their position with regard to bite." They can be used to adjust all types of malocclusions, including under and overbites, crooked teeth, open bites, and many other cosmetic and structural problems.
There are currently many types of braces available:
Metal Braces
The oldest type of braces are still the most widely used by dentists. They are also the most efficient and affordable option.
Ceramic or Clear braces
Almost invisible to the naked eye, since they blend in with the natural color of the tooth, they're as effective as metal braces and will not stain the surface of the teeth.
Gold Braces
Similar in strength to traditional metal braces, they offer an interesting visual alternative. Made of 24-carat gold-plated brackets and archwires, they are considerably more expensive and not widely available.
Lingual Braces
Not visible, since they are fitted behind the teeth. They are difficult to adjust to and many people suffer from cuts and sores while wearing them.
Invisalign
This new treatment can replace braces in milder cases that don't require an aggressive approach. Through 3D technology, dentists custom-design a series of aligners that are changed every two weeks to accommodate the movement of the teeth. Invisalign is more expensive than other treatments and is not recommended for very young children and certain orthodontic issues, including severe crowding, overbites or underbites. They are comfortable to wear and can be removed to eat, brush, and floss.