Today, there are two essential types of RFID tags and antennae available. In each of these categories, there are many types of tags, readers and antennae. There are two essential types of RFID technology which are described as ""Passive"" RFID and ""Active"" RFID. There are also variations of the two technologies. In short, Active RFID tags are battery charged and send a continuous or programmed interval message to a reader.