RFID, or Radio-Frequency Identification, refers to a specific type of asset tracker. It's a tag with a radio wave antennae that can transmit data for a short distance. The two other types of trackers are GPS units and barcodes. GPS units can send data anywhere in the world, while barcodes must be found and scanned. The RFID tag represents an in-between solution, as the scanner must be fairly close in order to register the asset: Between a few yards and 1.25 miles, depending on the type of RFID.