Add Sub Panel in Garage

The two Breakers in one space are exactly what it says on the tin They are separate Breakers with separate trip I have never seen double stuff

Tandem breakers are unique because they allow you to install two circuit breakers in the space of one standard breaker This means that you can have more

two slot shelving 1-inch breakers found in residential homes are typically single-pole breakers and occupy one slot on the panel Double-pole breakers are

two slot one energized wire and supplies 120V to a circuit They're generally rated 15 or 20 amps, occupy one slot on a breaker panel, and are the most common breakers