actually now that i read abit about it it's closely right but not excatly. planet is a heavy object orbiting star. however if the mass of the planet is enough, it will trigger the nuclear fusion in the core and at some point planet is then classified as a star. also a star can orbit a star.
object is a planet if following rules are met (international spacescience agency or something):
1. object is orbiting a star
2. object has enough mass to collapse close to spherical form
3. object is in "control" of its own orbit (meaning it orbits only the star, not other objects. this is why pluto is not classified as a planet, its orbit is heavily affected by the mass of neptune)