What's The Difference Between Astronomy and Astrophysics?

Astrophysics is a specialization in the field of astronomy (like gastroenterology is a specialization in medicine).

Broadly defined, astrophysics is the study of the physics of the universe. Whether it's applied to gravitational fields, high-energy particles, or celestial objects like stars and galaxies, astrophysics overlaps significantly with astronomy and can involve many foundational physics concepts like thermodynamics, electromagnetism, or quantum mechanics to name a few.

Astrophysics is a sub-discipline of Astronomy. Astrophysics is specifically concerned with physical processes and properties of objects beyond Earth. But since most modern astronomical research is concerned with physical / dynamical views of the Universe, most modern astronomy is really astrophysics.

There's not much difference any more. It used to be that astronomers would look at things and report their observations without attempting to interpret them, but you can't get away with that any more. Astronomers have a solid background in physics and math (and often programming) to interpret and predict the results they get and model the systems to see what's going on. An astronomy major would require a bit less physics than an astrophysics major, but anyone who wants to be an astronomer and do research in the field should be majoring in physics. Many astronomers are also physicists.