The tai chi form is one long movement in which the body explores a variety
of different shapes.
It serves to train mind and body to move in the tai chi way.
For beginners, the form is split into segments referred to as 'postures'.
The definition of the word posture is: "the way in which a person stands or
moves".
Unfortunately, for many people the word also has the connotation of fixity
which can be very misleading.
Tai chi form is not yoga - we want to move - not hold a position. Tai chi is
the movement itself rather than a sequence of held shapes.