  Galactic winds constitute a primary feedback process in the ecology and
evolution of galaxies. They are ubiquitously observed and exhibit a rich
phenomenology, whose origin is actively investigated both theoretically and
observationally. Cosmic rays have been widely recognized as a possible driving
agent of galactic winds, especially in Milky-Way like galaxies. The formation
of cosmic ray-driven winds is intimately connected with the microphysics of the
cosmic ray transport in galaxies, making it an intrinsically non-linear and
multiscale phenomenon. In this complex interplay the cosmic ray distribution
affects the wind launching and, in turns, is shaped by the presence of winds.
In this review we summarize the present knowledge of the physics of cosmic rays
involved in the wind formation and of the wind hydrodynamics. We also discuss
the theoretical difficulties connected with the study of cosmic ray-driven
winds and possible future improvements and directions.
