  The role played by torsion in gravitation is critically reviewed. After a
description of the problems and controversies involving the physics of torsion,
a comprehensive presentation of the teleparallel equivalent of general
relativity is made. According to this theory, curvature and torsion are
alternative ways of describing the gravitational field, and consequently
related to the same degrees of freedom of gravity. However, more general
gravity theories, like for example Einstein-Cartan and gauge theories for the
Poincare and the affine groups, consider curvature and torsion as representing
independent degrees of freedom. By using an active version of the strong
equivalence principle, a possible solution to this conceptual question is
reviewed. This solution favors ultimately the teleparallel point of view, and
consequently the completeness of general relativity. A discussion of the
consequences for gravitation is presented.
