It is a type of science that looks at forces and interactions.
The physics4kids website tells us that "everything in the universe has an effect on every other thing. Physicists study those effects.
Physics is a science that relates to all other sciences: Chemistry, Biology, Geology, Astronomy, Meteorology and Engineering.
Everything on Earth, everything in the solar system, the galaxy and the universe moves and interacts and forces play a big part in that.
Motion, heat, electricity and light are all studied by physicists.
Take a look at the video clip on work from NASA.