  The spectral energy distributions (SEDs) of galaxies are shaped by nearly
every physical property of the system, including the star formation history,
metal content, abundance pattern, dust mass, grain size distribution, star-dust
geometry, and interstellar radiation field. The principal goal of stellar
population synthesis (SPS) is to extract these variables from observed SEDs. In
this review I provide an overview of the SPS technique and discuss what can be
reliably measured from galaxy SEDs. Topics include stellar masses, star
formation rates and histories, metallicities and abundance patterns, dust
properties, and the stellar initial mass function.
