Since you asked: Yes, I have four of them and they all work, and all were purchased about 18 months ago. Two, so far, required a battery replacement, but nothing else.
As Rudegar has already mentioned, when your AirTag is outside the Bluetooth range (~30-40') of your iPhone, it will use the Apple Find My network. That network consists of literally millions of other iPhones. If one of those get within Bluetooth range of your tag, it will receive the tag's ID, and then, send it along with the phone's GPS location, to the Apple servers over an Internet connection. In turn, this is where the Find My app on your phone gets these updated locations from.