Car Electronics And Audio

My brake lights aren't lighting up when I step on the brake pedal. All of my other rear lights work fine. My brake lights and rear/turn signal lights share the same (dual filament) bulb. The rear lights and turn signal lights both work. The upper brake light in my rear window works. I have replaced all the bulbs and checked all my fuses.

By doing some research online, I'm thinking it's the brake switch by my pedal. I was able to locate the switch. However, I have no prints, or working knowledge of the switch. I don't want to mess around with it without knowing what I'm doing.

Can anyone give me info on how it works and how to test or replace it? Or perhaps direct me to a website that has the information readily available.

I have experience with electronics so don't worry about technical explanations. I'll understand what you're talking about.

Thanks! Sorry for the long read.