Hello, I have a 2001 road king classic, my headlight appears to have 2 bulbs, can some tell me what the small lower “bulb” is?

 

That's known as a 'position lamp'. Essentially it's a type of parking light. They're required in some European countries. Google "Harley Position Lamp" for details..

It shows up in wiring many HD wiring diagrams.

 

that's the first I've seen of that... interesting?

 

I always thought that was a UK option. My Triumphs had it