This chapter introduces the reader to the different parts that make up a radiofrequency identification (RFID) system. RFID systems contain more elements in addition to the transponder and interrogator. In addition to the transponders, the interrogators, and their antennas, the RFID system requires a host computer connected to the interrogator. This host computer provides a certain level of intelligence and acts like the interface between the RFID system and the ultimate application. A functional classification of RFID transponders is based on their electronic product code (EPC) class. EPC is the application of one specific type of RFID technology within the consumer packaged goods industry. The initial users of RFID systems found systems operating in the low-frequency (LF) range followed a few years later by systems operating in the high-frequency (HF) range. RFID systems operating in the HF range can support higher read rates than LF systems.