Orthodontics is when the teeth are straightened or moved in order to improve the appearance of your smile by correcting the alignment of your teeth and the way you bite together. An incorrect bite can lead to long term dental problems and even jaw and head pain. By straightening the teeth, you also help to prevent tooth decay and gum diseases as straighter teeth are easier to clean.
Orthodontic braces are either fixed or removable. Fixed braces consist of brackets and bands which are cemented (glued) to your teeth which hold flexible wires in place. In turn, these wires exert pressure on your teeth gently moving them into their correct position over the course of your treatment. Removable braces can be taken in and out of the mouth. It has delicate wires and springs attached which move the teeth using gentle pressure. These are used for less complex cases or in conjunction with fixed Braces as part of a combined treatment.
Brackets for Orthodontics Image from Wikipedia.
Hawley retainers are the most common type of retainers. This picture shows retainers for the top and bottom of the mouth. Image from Wikipedia.