Water. Notice the threads are standard hose bib threads (forget what they’re called, it’s not pipe thread, just similar).
It uses a key to operate it, helps prevent average jerks from just turning it on. (These keys are widely available for about $5)
Edit: the little cap is for freeze protection. It’s part of a mechanism to vent water from the last foot of the pipe and bib, so there’s no water in it to freeze when the valve is closed.
You can find these spigots on buildings all over the place. Sometimes they are locked behind a panel that you can also open with that same tool. Great for nomads.
Water. Notice the threads are standard hose bib threads (forget what they’re called, it’s not pipe thread, just similar).
It uses a key to operate it, helps prevent average jerks from just turning it on. (These keys are widely available for about $5)
Edit: the little cap is for freeze protection. It’s part of a mechanism to vent water from the last foot of the pipe and bib, so there’s no water in it to freeze when the valve is closed.
So only above average jerks can turn it on?
Would you want any other type of jerk playing with your sillcock?
They are called sillcock keys. They come in a few different sizes so you’ll often see 4-way tools like this one: https://www.homedepot.com/p/Husky-4-Way-Sillcock-Key-16PL0129/304217572
You can find these spigots on buildings all over the place. Sometimes they are locked behind a panel that you can also open with that same tool. Great for nomads.