A synchronous orbit is an orbit in which an orbiting body (usually a satellite) has a period equal to the average rotational period of the body being orbited (usually a planet). Or in smaller words, the orbit above and the spinning planet below, go around once in the same amount of time. It orbits in the same direction of rotation as that body. So if you were on the orbiting body, you would always see the same side of the body being orbited. Or if you were on the body being orbited, the orbiting body would stay in the same part of the sky. Geostationary orbit is the most common kind.