RFID attaches a tag, an antenna and a chip holding an identifier, to an object, and a reader retrieves that identifier over radio. Passive tags have no battery; they harvest energy from the reader’s field, which keeps them cheap enough to put on individual garments or medicine boxes. UHF tags can be read by the hundred from several meters away, which is what makes retail inventory counts and pallet-level supply chain visibility practical.
RFID is often called the original Internet of Things, since it gave inert things a digital identity before they had electronics of their own. Its limits are that a tag only speaks when a reader asks, so it reports presence rather than condition, and that metal and liquids interfere with reads. NFC is a related short-range technology built for two-way interaction with phones.
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