Bluetooth sensor tags and sensor beacons are essentially the same thing. The terminology of tags vs beacons stems from how they are used. If the devices are fixed, they tend to be called beacons and if they are placed on assets or people they tend to be called tags because they are tagging things and people. However, the terminology is interchangeable, irrespective of the use.
The use of the term tags also comes from the use in RFID, barcode and UWB devices that can also be used to uniquely identify devices.
Bluetooth sensors can be used in two ways, either via connection-less advertising or having another Bluetooth device connect and examine values. This is explained further in our article on Using Bluetooth Wireless Sensors.
Tagging implies locating. However unlike other technologies, devices can do a lot more than just locating and can detect movement (accelerometer), temperature, humidity, air pressure, light and magnetism (hall effect), proximity, heart rate and fall detection.
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Using Beacons, iBeacons for Real-time Locating Systems (RTLS)