Sorry its a 2004 645ci

What is the purpose of the middle bulb in the headlights? The low and high beams work off the xenon outside light. When i put the high beams on by pushing the lever forward,nothing happens,
and if i pull it back the lights come on. Is it just to flash someone? I would have to hold the lever back to keep them on, which is dumb.

I searched almost 100 pages on e-bay and there is no owners manual out there other than online. Well i take that back, i found one for $299. thats nuts!!