Taillight bulbs, confused about how they work Options

[RoadRage]

Today I was fiddling with the car and I took one of my tail lights out and noticed there is a second brake and light bulb in the casing, and I never saw it work, I thought maybe it was meant to, so I replaced the bulb but it still was not working, So im writing to ask whats the go?

After doing some research (Looking at some pics on this forum) I saw that the OEM tail lights seem to have only 1 light working on each side, but the JDM tails have 2 brake lights.

Im hoping to get some JDM tails soon, but until then, I want to roll with 2 lights working, because it seems like a wasted light if its un-used and in my opinion two looks cooler,

I had a play and switched around where the light goes but for now im just left with the decision about which way should my lights work for now until I figure out how to get both to work



Was the inside bulb (the right tail light in the photo, that I switched) never meant to work and it was always meant to be 1 light only (left light) or do I need some wiring harness of some sort?