If you're new to Bryce and asking what a path does (and forgive me if I misunderstood) the easy way to say is that its a predefined 'road' through your bryce scene that an object can be put on and told to follow. Can be the camera, or a sphere, or whatever. So if you use a preset path, or make one yourself, and put a sphere on it and set your animation appropriately, bryce will make a movie with your sphere moving along that path. A simple circle path around a large sphere with a smaller sphere moving along it will result in a movie that shows a moon orbiting a planet. Paths are essential to making animations, though you can animate without them.