2 Answers

RFID stands for Radio-frequency identification (RFID). It is wireless non-contact use of radio-frequency electromagnetic fields to transfer data, for the purposes of automatically identifying and tracking tags attached to objects.

RFID Tagging is very useful in tracking wildlife, identifying livestock and pets. People are also increasingly tagged  for medical and identity purposes. Many, if not all items in stores have id tags that correspond with a data base tracking system that allows the compilation of purchases, trends, thefts and buying habits over a wide range of variables. This data is mostly used for stocking and reordering of purchased articles.

Some consider data modeling as invasive of privacy, but you usually identify yourself when making purchases in some way. There is a lot of information going through these systems every day and all of it is definable in association with who you are in these systems. It is why the USA has the highest arrest and conviction rate in the world.