Theoretical cosmology is a branch of astrophysics that focuses on understanding the universe's structure, origin, and evolution through mathematical models and simulations. It seeks to explain phenomena such as the Big Bang, cosmic inflation, and the large-scale distribution of galaxies. Researchers in theoretical cosmology use concepts from general relativity and quantum mechanics to develop theories about the universe's fate, including scenarios like dark energy and black holes. By analyzing cosmic microwave background radiation and other observational data, they aim to refine our understanding of the universe's fundamental properties.