Self-gravitation is the gravitational force of an object on itself, i.e., on other portions of itself. It is the force that keeps stars and planets intact, and presumably galaxies, galaxy clusters, and many clouds; these are termed self-gravitating bodies. It does not affect small, solid objects such as a table or chair: at such a small scale, the gravity of chair material on portions of the chair is so small as to be immeasurable and certainly beyond practical use; such objects are held together by chemical bonds. A meteoroid is presumably not held together by self-gravitation but for such objects, considering larger sizes and masses, there comes a point where self-gravitation holds it together, and even loose material still remains with the object if undisturbed, i.e., does not drift away.
Much physical phenomena is modeled ignoring self-gravitation, in situations where it is not significant. For some astrophysical phenomena, whether to include it in a model is a real issue.