  Brown dwarfs are commonly regarded as easily-observed templates for exoplanet
studies, with comparable masses, physical sizes and atmospheric properties.
There is indeed considerable overlap in the photospheric temperatures of the
coldest brown dwarfs (spectral classes L and T) and the hottest exoplanets.
However, the properties and processes associated with brown dwarf and exoplanet
atmospheres can differ significantly in detail; photospheric gas pressures,
elemental abundance variations, processes associated with external driving
sources, and evolutionary effects are all pertinent examples. In this
contribution, I review some of the basic theoretical and empirical properties
of the currently known population of brown dwarfs, and detail the similarities
and differences between their visible atmospheres and those of extrasolar
planets. I conclude with some specific results from brown dwarf studies that
may prove relevant in future exoplanet observations.
