What is physics? Physics is the foundation of science. It is the scientific study of matter and energy and how they interact with each other. But because everything around us is made up of matter and energy, then physics really explains how things work, from the smallest particles to the structure of the universe.
If you have to ask "why study physics," then you don't get science. But if you want to truly understand the world around you, then welcome to our universe. You'll enjoy it here.