There are many types of stars that exist in the universe. Stars can be categorized based on their size, composition, temperature, and stage of life. The main types of stars discussed are protostars, T Tauri stars, main sequence stars, red giants, white dwarfs, red dwarfs, neutron stars, black holes, and supergiant stars. Each star type has distinct characteristics that define it, such as their size, composition, or life cycle stage.