Dwarf spheroidal galaxies are small, round galaxies that contain a relatively low number of stars compared to larger galaxies like Milky Way. They are typically composed of older stars and have little to no new star formation. Their spherical shape and low luminosity make them difficult to detect. These galaxies are often found in the vicinity of larger galaxies and can be considered satellite galaxies. Dwarf spheroidal galaxies are important for studying the formation and evolution of galaxies, as they provide insights into the early universe and the role of dark matter in galaxy formation.