A physicist studies how the universe works. Experimental physicists do laboratory work to discover or verify laws of nature. Theoretical physicists come up with mathematical models to describe those laws. Physicists study problems ranging from how the smallest possible particles behave to how galaxies form. We look for ways to describe how water flows through pipes, how electric circuits work, how light splits into colors, why magnets attract certain types of metals, what keeps the sun hot, what keeps molecules from falling apart, how space bends or curves, and millions of other problems.
Physics also combines with other disciplines.
Applied math uses equations to predict what will happen in real-life systems. It always amazed me that equations can describe what happens in the real world. There are many other areas where physics combines other subjects such as biophysics, chemical physics, and geophysics. My own specialty is the branch of chemical physics that uses quantum mechanics to describe how atoms and molecules behave. Physicists are curious about why the universe works the way it does.