In space, the term commonly used to refer to the distance between two objects is "interplanetary space" or "interstellar space," depending on the context. These terms indicate the space between planets within a solar system or the space between stars within a galaxy, respectively.
The vast majority of space is empty, with extremely low densities of matter, particularly in interstellar space. It is mostly a vacuum, devoid of significant concentrations of gas, dust, or other material. However, even in seemingly empty regions, there can still be extremely sparse matter, such as individual atoms or particles.
It's important to note that the distance between objects in space can vary widely, ranging from relatively close distances within a planetary system to vast distances between stars or galaxies. The scale of these distances is often measured in astronomical units (AU), light-years, or parsecs, depending on the context.