Theoretical stars are hypothetical celestial objects that scientists use to explore the possibilities of stellar evolution and the universe's structure. These stars are not directly observed but are modeled using mathematical equations and simulations to understand their potential characteristics, such as mass, temperature, and lifespan. Researchers study various types of theoretical stars, including black holes, neutron stars, and supernovae, to predict how they might form and behave under different conditions. By examining these models, astronomers can gain insights into the life cycles of real stars and the dynamics of galaxies, enhancing our understanding of the cosmos.