Used to store pressure from the hydraulic braking system and function as a backup pressure supply in the event of pump failure. Upon start up, both lights should extinguish once up to pressure. Pressure loss would indicate a faulty pump or a leak in the system, occaisonally around the valve body.
With the engine off, new spheres should have approximately 30-40 pumps until braking is lost. If you are experiencing pressure issues of any kind it is advised that the spheres are replaced.