1. Matter: This refers to anything that has mass and occupies space. It encompasses everything from the smallest subatomic particles to the largest galaxies. Physics studies the properties of matter, how it interacts, and how it changes.

2. Energy: This is the ability to do work. It exists in many forms, such as kinetic energy (motion), potential energy (position), heat, light, and sound. Physics explores the various forms of energy, how they transform and transfer, and how they relate to matter.

So, in short, physics studies the fundamental building blocks of the universe (matter) and the forces that govern them (energy).