Cool stars refer to stars that have lower surface temperatures compared to hotter stars, such as the Sun. They are typically characterized by their red or orange color and are less luminous than hotter stars. Cool stars include spectral classes K and M, with temperatures ranging from about 2,000 to 6,000 Kelvin. Research on cool stars focuses on understanding their physical properties, evolution, and behavior. This includes studying their magnetic fields, variability, and activity levels, as well as investigating how cool stars impact the habitability of planets in their orbit. Cool stars also play a crucial role in the study of stellar astrophysics and the overall structure and dynamics of the Milky Way galaxy.