A synchronous resonance is an orbit around a body such that the orbiting body remains in one position over the orbited body because the orbit circles the body at the same rate that the body is rotating. Such orbits are used to make satellites apparently "sit in one spot" above the surface of the Earth, e.g., for communication.
The term geostationary orbit refers to such an orbit around the Earth and a geostationary orbit refers to one that has the same orbit period but is not aligned with the Earth's equator and/or is eccentric, so it moves in a daily pattern relative to the surface of the Earth.
Charon orbits Pluto in a synchronous orbit. In such natural cases, tidal locking is a contributing factor, e.g., involving some asymmetry in Pluto's mass. The two are mutually tidally locked, each rotating so as to face the other. Such rotation of a tidally locked body is termed synchronous rotation, i.e., the rotation is synchronized with the orbital period.