A binary star is a system of 2 stars where the 2 stars orbit around each other. They actually orbit around their common barycenter. I actually have no idea what that means; I just like the idea of 2 stars orbiting...
... around each other. Who knew stars could be star-crossed lovers? Sometimes double stars are mistaken for binary stars, but those are actually just stars that appear closer together due to their distance from earth or wherever the picture's being taken. Google Visual Binary Stars if you want to try to see these from your backyard.
Binary star system
“These stars will always be in each other's orbits. So cute!”