RFID(Radio Frequency Identification)sensor uses the power of radio signals to read important information from RFID tags. So when an RFID tag comes in the range of any RFID reader, the reader can read whatever the tag says by inducing the radio signals into the tag to power it. It then receives a feedback from the tag which contains a specific information embeded in it.
It is used it so many applications in logistics, door and home security, object and product tracking, access control and many more. Get yourself more resources and tutorials about this in the Aaenics community.