Due to their intrinsic faintness, brown dwarfs are often challenging to detect--whether as isolated free-floating objects in the solar neighborhood, or as companions to more massive, brighter stars. As a result, the physical and population properties of brown dwarfs remain poorly constrained relative to those of main sequence stars. However, the completion of several sensitive large-area imaging surveys over the past decade and the fast-paced development of high-contrast imaging technology are rapidly enhancing our empirical understanding of substellar objects.
I will overview recent results on the population properties and mass function of substellar objects, differentiating between isolated brown dwarfs and brown dwarf companions to stars. I will also draw parallels between brown dwarfs and known extrasolar planets, and will in particular present how brown dwarf companions to stars can inform on the atmospheric properties of hot Jupiter-type exoplanets. I will conclude by making projections for the detection rates of extremely cool brown dwarfs in several on-going and planned wide-field imaging surveys, and will compare these to the expected detection rates of planetary-mass companions in future extremely high-contrast imaging surveys.