What is inside the orbit?

Could you please elaborate on what exactly lies within the confines of an orbit? Are we referring to celestial bodies, such as planets and moons, that revolve around a larger object like a star? Or is there something more abstract, like the invisible forces that govern these movements? Understanding the intricacies of an orbit and its contents is crucial for astronomers and astrophysicists alike, so I'm curious to know what specific insights you can provide on this topic.