Astronomers believe most stars are part of binary systems rather than solo systems. A binary system means two stars orbiting each other.
They think Pluto is somewhat of a binary object with its inordinately large moon. The center of gravity between the two is outside Pluto itself.
Similarly, in a binary star system you have two stars going around a center of gravity that lies somewhere between the two of them but outside the sphere of either.
This happens a lot in space. Even here on Earth our own moon is relatively large. This is one of several explanations for the Earth’s wobble (along with droughts) and certainly why the moon wobbles. When that wobble becomes such that essentially both objects wobble around each other that’s a binary system.
Such bodies can be two stars, two planets or even two black holes that revolve around each other. Even a galaxy behaves in such a way that the stars orbit a center of gravity outside of themselves.
Recently astrophysicists have even wondered whether our own sun is part of a binary system revolving around an unknown brown dwarf hiding somewhere in the Oort Cloud.
But binary systems are only part of the story. Out there where no man has gone before there are trinary systems or even more.
The universe is not well understood though we like to think we know more than we do. There are great mysteries out there we may never understand.