  The Wigner distribution function and its spatial-angular moments
(intensity-moments) are known as efficient instruments for characterization of
complex quasimonochromatic light beams and their transformations. In this
paper, the generalization of the WF-based approach to spatio-temporal (ST)
light fields (wave packets, short pulses) is considered. It is shown that the
ST intensity moments are related with the important characteristics of the
wave-packet structure, especially, with the transverse orbital angular momentum
(OAM) being a specific feature of the ST optical vortices (STOV). The ST
moments' transformations in a paraxial optical system obey simple and unified
rules involving the ray-transfer ABCD-matrix of the system. On this base, and
with simple examples of the OAM-carrying optical pulses, the schemes and
mechanisms of the STOV generation and transformation are presented. Examples of
non-vortex ST wave packets with the transverse OAM, their possible realizations
are discussed as well as the relations between the OAM and the visible pulse
rotations. The regular and unified formalism, developed in this paper, can be
generalized and applied to more complex situations where the ST field
propagates through inhomogeneous and random (scattering) media.
