Barycenter

In Astronomy the term barycenter refers to the location of the centre of mass of a pair of bodies that orbit one another.

Because Planet Earth is about 80 times more massive than Luna, our moon, the barycenter of the Earth-Moon system is located inside the Earth. Pluto and its moon Charon are closer in mass, and their barycenter of the Pluto-Charon system lies between the two bodies.