Brown dwarfs are celestial objects that are larger than planets but smaller than stars. They form in a similar way to stars, through the gravitational collapse of gas and dust, but they do not have enough mass to sustain nuclear fusion in their cores. As a result, they emit very little light and heat, making them difficult to detect. These objects typically have masses between about 13 and 80 times that of Jupiter. Brown dwarfs can be found in various regions of space, often in star-forming regions, and they play a crucial role in understanding the formation and evolution of both stars and planets.