Gait

When you watch how most people walk, it is quite alarming. Their steps are often very heavy and their legs are locked and immobile. 
There is a sense of clumsiness.

People frequently walk in an agitated manner; over-striding and erratic. The lower back is inflexible and the sacroiliac does not move correctly.

Tai chi chuan re-trains the body to move naturally and freely.
As a student moves through the syllabus, they are challenged with increasingly sophisticated stepping patterns. This leads to the easy, relaxed grace of a dancer or a large cat.