Two common excessive curvatures of the spine are kyphosis and lordosis. Kyphosis is when the upper back and shoulders are overly rounded forward. Lordosis is when the bones of the spine appear to be forward when seen from the side; this is most commonly seen in lumbar lordosis where the concave part of the low back has too much curve.
Kyphosis and lordosis have a variety of causes, but in today's world many of us sit too much and exercise too little, so muscular weakness and the resulting physical imbalances contribute greatly to these problems.
Computer and desk worker hunchback is an example of a kyphosis-like problem that reflects a weakness in the back muscles, especially the back extensor muscles that hold the upper back upright. Swayback is a layperson's term for lumbar lordosis. It is often associated with weak abdominal muscles that are not able to hold the low back and pelvis in their neutral position where the pelvis is like a level bowl. Instead, weak abdominals allow the pelvic bowl to tip forward creating excessive curve at the back.