  The winds of cool luminous AGB stars are commonly assumed to be driven by
radiative acceleration of dust grains which form in the extended atmospheres
produced by pulsation-induced shock waves. The dust particles gain momentum by
absorption or scattering of stellar photons, and they drag along the
surrounding gas particles through collisions, triggering an outflow. This
scenario, here referred to as Pulsation-Enhanced Dust-DRiven Outflow (PEDDRO),
has passed a range of critical observational tests as models have developed
from empirical and qualitative to increasingly self-consistent and
quantitative. A reliable theory of mass loss is an essential piece in the
bigger picture of stellar and galactic chemical evolution, and central for
determining the contribution of AGB stars to the dust budget of galaxies. In
this review, I discuss the current understanding of wind acceleration and
indicate areas where further efforts by theorists and observers are needed.
