What am I doing in AP Physics 1

AP Physics 1 is just algebra-based mechanics. So that includes kinematics, energy, momentum, circular motion, gravitation, simple harmonic motion, and rotation. If you've never taken a physics class before, you could probably benefit from gaining familiarity with the relevant equations the course uses. If you can use (or even just conceptualize how to use) each one of the equations on the physics 1 equation sheet, you'll be in good shape.

I suppose if you're shaky in math or problem solving, you'd benefit from practicing Physics 1 type problems over the summer. The big emphasis in science AP's is mastery of the subject matter combined with the ability to quickly solve problems and design experiments.