A beacon is a small Bluetooth radio transmitter.

It’s kind of like a lighthouse: it repeatedly transmits a single signal that other devices can see. Instead of emitting visible light, though, it broadcasts a radio signal that is made up of a combination of letters and numbers transmitted on a regular interval of approximately 1/10th of a second. A Bluetooth-equipped device like a smartphone can “see” a beacon once it’s in range, much like sailors looking for a lighthouse to know where they are.