Scoliosis is commonly known as a curvature of the spine. Scoliosis is not seen as a diagnostic term but more as a description of a sideways curvature accompanied by a vertebral twist. Scoliosis is rarely found as a significantly debilitating condition.
The curve of the spine in healthy individuals is meant to be vertical or straight up and down when looking from behind. A healthy resting neutral spine from a side view has a mild curve inwards at the neck (Cervical spine), a mild rounded curve at the mid-back area (Thoracic spine), and a mild curve inwards in the lower back (lumbar spine).
In individuals with a scoliosis, a curve to the left or the right can be seen when looking from behind. Scoliosis Australia explains that most scoliosis or spine cures are seen in the thoracic spine. Most curves are quite mild and only 2 to 3% have curves of 10 degrees or higher (moderate curves). Of these less than 0.1% have curves of 40 degrees or higher (http://www.scoliosis-australia.org/).