  Galactic globular clusters, which are ancient building blocks of our Galaxy,
represent a very interesting family of stellar systems in which some
fundamental dynamical processes have taken place on time scales shorter than
the age of the universe. In contrast with galaxies, these clusters represent
unique laboratories for learning about two-body relaxation, mass segregation
from equipartition of energy, stellar collisions, stellar mergers, and core
collapse. In the present review, we summarize the tremendous developments, as
much theoretical as observational, that have taken place during the last two
decades, and which have led to a quantum jump in our understanding of these
beautiful dynamical systems.
