  Over the past 10 years abundant evidence has emerged that many (if not all)
stars are born with circumstellar disks. Understanding the evolution of
post-accretion disks can provide strong constraints on theories of planet
formation and evolution. In this review, we focus on developments in
understanding: a) the evolution of the gas and dust content of circumstellar
disks based on observational surveys, highlighting new results from the Spitzer
Space Telescope; b) the physical properties of specific systems as a means to
interpret the survey results; c) theoretical models used to explain the
observations; d) an evolutionary model of our own solar system for comparison
to the observations of debris disks around other stars; and e) how these new
results impact our assessment of whether systems like our own are common or
rare compared to the ensemble of normal stars in the disk of the Milky Way.
