For many of us, using a key to start a car, a card to access a building or room, using ski lifts on a winter sports holiday and validating a bus or underground ticket have become part of our daily routine. Without always realising it, we use automatic data capture technology that relies on radio-frequency electromagnetic fields. This technology is known as Radio-Frequency IDentification or RFID.

Just as people use RFID as they go about their daily lives, objects also use this technology, as they transit from manufacture to storage and finally the point of sale. Like us, they also carry RFID tags. The difference between objects and ourselves is that they don’t "voluntarily" present their RFID tag or card when asked. These tags are therefore read in very different conditions and often require greater detection distances.

RFID (Radio Frequency Identification) can be defined as follows: Automatic identification technology which uses radio-frequency electromagnetic fields to identify objects carrying tags when they come close to a reader.

However, RFID cannot be reduced to one technology. RFID uses several radio frequencies and many types of tag exist with different communication methods and power supply sources.
RFID tags generally feature an electronic chip with an antenna in order to pass information onto the interrogator (also known as a base station or more generally, reader). The assembly is called an inlay and is then packaged to be able to withstand the conditions in which it will operate. This finished product is known as a tag, label or transponder. 
The information contained within an RFID tag’s electronic chip depends on its application. It may be a unique identifier (UII, Unique Item Identifier or EPC code, Electronic Product Code, etc.). Once this identifier has been written into the electronic circuit, it can no longer be modified, only read. (This principle is called WORM Write Once Read Multiple). Some electronic chips have another memory in which users can write, modify and erase their own data. These memories vary in size from a few bits to tens of kilobits.