An M-dwarf, also known as a red dwarf, is a type of small and cool star that falls within the spectral class M. These stars are the most common in the universe, making up about 70-80% of all stars. M-dwarfs have low temperatures, typically between 2,400 and 3,700 Kelvin, and they are much dimmer than larger stars like G-type stars, which include our Sun. M-dwarfs have a long lifespan, often lasting tens of billions of years, due to their slow rate of nuclear fusion. This longevity makes them interesting targets in the search for exoplanets and potential habitable zones, as their stable environments may support life over extended periods.