co-orbital configuration

A quasi-satellite is an object in a specific type of co-orbital configuration (1:1 orbital resonance) with a planet where the object stays close to that planet over many orbital periods.

In astronomy, a co-orbital configuration refers to two or more celestial objects (such as asteroids, moons, or planets) that orbit at the same, or very similar, distance from their parent object as each other, i.e. they are in a 1:1 mean motion resonance.