Dental braces are wires that are held together by brackets glued to the permanent teeth. The wires and brackets may be made of metal or other materials. Each week or month (or other time the orthodontist decides) the braces may be checked, cleaned, or changed into a tighter wire.
Braces are an orthodontic device. They are to make the teeth straight, and to correct problems in a person's bite. There are many natural problems which occur to the way teeth fit together, but not everyone needs or will need braces.
However, the use of braces is quite common, even when they are not medically necessary. Their cosmetic use for young females is more common in countries with first world economies. To overcome the visibility of traditional metal braces, there are now nearly transparent braces. Sometimes braces are possible behind the teeth, and so are not in view.