A BLE beacon is a small device that broadcasts a Bluetooth Low Energy signal so nearby phones can detect it. Beacons mark a place or a provider without connecting to anything.
The longer version
A BLE beacon does one thing: it repeats a small identifying broadcast over Bluetooth Low Energy. Phones in range hear it and can act on it. Because the beacon only transmits, it is cheap, low power, and simple to place on a counter, a vehicle, or a shelf.
Beacons are a common way to signal presence, but a plain beacon setup usually stops at detection. The phone notices the beacon and perhaps opens a message. Turning that into a trustworthy payment needs a way to resolve the nearest match and route money safely.
In a proximity payment method the beacon is only the broadcaster. The phone reports what it hears to a central server, the server resolves the nearest pairing, and the transaction routes server side. The beacon never handles the payment or connects to the phone.
The Parousya method
A BLE beacon can serve as the provider's broadcaster in the Parousya method. The difference from a plain beacon deployment is what happens next: the server resolves the nearest pairing and routes the transaction, so detection becomes a safe payment.