Dwarf stars are small, dense stars that have a mass less than that of the Sun. They can be classified into different types, including white dwarfs, brown dwarfs, and red dwarfs. These stars typically have low luminosity and can be found in various stages of their life cycle. White dwarfs are the remnants of stars that have exhausted their nuclear fuel, while brown dwarfs are substellar objects that never ignited nuclear fusion. Red dwarfs are the most common type of star in the universe, known for their long lifespans and low temperatures.