This document presents an overview of radio frequency identification (RFID) systems. It outlines the key components of an RFID system including tags, readers, and a computer system. It describes how RFID works and provides examples of applications such as inventory management, library tracking, and human/animal tracking. The document also discusses some disadvantages of RFID including interference from metals and potential issues from repeated tag interrogation. It concludes that RFID technology is expanding into new areas and capabilities.