It is a 110v 20amp outlet. It works as a regular 110 outlet but there are some appliances that need 20amp. My espresso machine is one for example. Some countertop ovens also use 20amps.

Example of outlet

Good luck!

I have one o use for my pressure washer. That’s probably why it’s in the garage.

Corded appliances that need more than 15 amps have plugs with the "T" configuration you see on your outlet. This is a safety measure to prevent you plugging those appliances into a "standard" outlet. Corded appliances that draw less than 15 amps can be plugged into these outlets as well. Before I used that outlet for a 20 amp appliance, I would verify it's on a 20 amp breaker. It's illegal to install a 20 amp outlet on a circuit controlled by a 15 amp breaker, hopefully for obvious reasons.

I have a similar receptacle in the master bedroom where it was used for a window A/C unit before we installed central A/C.

Bruce

Having a 15A breaker and a 20A outlet is actually relatively harmless. You just end up getting nuisance trips.

It's the wiring that you need to be worried about. If you have a 15A breaker, there also is a good chance that you have 14 gauge wiring. That's not enough to safely carry 20A.

So, the dangerous scenario is somebody switching out breakers and outlets but leaving the wiring unchanged. And unfortunately, that can go undetected quite easily. Many homeowners can't really tell 14 gauge from 12 gauge copper wire.