Radio frequency identification, or RFID, is a generic term for technologies that use radio waves to automatically identify different objects. There are several methods of identification, but the most common is to store a serial number that identifies a person or object, and perhaps other information, on a microchip that is attached to an antenna. The chip and the antenna together are called an RFID transponder. The reader converts the radio waves reflected back from the RFID tag into digital information that can then be passed on to computers that can make use of it. (From http://www.rfidjournal.com/articles/view?1339)
While Barcode requires line of site to identify the object, with RFID Tracker one can just scan the tagged object remotely from a few meters away. RFID stickers come in same sizes as barcode stickers and can also be attached to any kind of items, like documents, tools, books, wallets, sunglasses, photo-equipment, etc.