Brown dwarfs are substellar objects that possess mass exceeding the largest gas giant planets but are insufficient to sustain stable hydrogen fusion in their core like true stars. These objects are primarily composed of hydrogen and helium, and their physical properties and evolutionary paths differ significantly from those of main-sequence stars. Because they lack the core temperature and pressure required for sustained fusion, they gradually cool and dim over astronomical timescales. Their classification places them in an intermediate regime of celestial bodies, making them crucial for understanding the boundary between planet formation and the formation of low-mass stars.