ORTHODONTICS is the process of straightening teeth with the help of an appliance ( wires etc). Any child or adult might require orthodontic treatment who has teeth that are:

Crooked
Alignment and Spacing
Protruding
Irregular
With gaps in between
In the wrong bite

An orthodontic treatment involves putting a wire/brackets on your teeth and regular visits (once a month mostly) for tightening/changing the wire. Each sitting takes only 10-15 minutes.

How long will my treatment take?
Treatment time depends on

Severity of Problem
Age of patient
Regularity of visits
Type of bone/pace of movement of teeth
The inclusion of chin caps/headgear or any myofunctional appliance treatment prior to braces
Teeth stuck deep in the jaw.

Therefore treatment time can vary between 1-3 years. On an average it takes about 16-18 MONTHS (1-1.5 years)