Eddystone beacons are Bluetooth LE devices that repeatedly send out Google-defined Eddystone advertising. There are four variants; UID - similar to iBeacon sending out a unique id, URL - sends a web address, EID - sends a time varying unique id for secure applications, TLM - sends out status information.

Google also flirted with the idea of having standard software, Eddystone Configuration GATT Service, in all beacons, accessible via standard (Eddystone) GATT services. They provided a standard implementation but there was poor takeup by manufacturers.

While beacons can send out Eddystone-URL, this became redundant when Google dropped Nearby detection of this type of beacon.

Eddystone Specifications (GitHub)
Intro to Eddystone
iBeacon and Eddystone - Beacon Basics - Kontakt.io
Is it Possible To Use One App to Manage All Beacons?
Open Source Eddystone Beacon Firmware
Google to Stop Serving Android Nearby Notifications