What are the differences between astrophysics and cosmology?
Cosmology is actually the study of birth of the universe, the changes and evolution and the fate or end of the universe. Cosmology is a subject as whole study of universe.
On the other hand, Astrophysics is the study individual things in Universe like the celestial bodies, Cosmic Microwave Background, Black holes, etc. Astrophysics is actually a really broad subject consisting of many subjects like Quantum Mechanics, Special and General Relativity, etc.