Non-fungible tokens, or NFTs, have exploded onto the digital art scene this past year. Proponents say they are a way to make digital assets scarce, and therefore more valuable. WSJ explains how they work, and why skeptics question whether they’re built to last. Photo Illustration: Jacob Reynolds/WSJ

A non-fungible token is a special type of cryptographic token which represents something unique. NFTs are called non-fungible because they are not mutually interchangeable, since they contain unique information, although it is possible to mint any number of NFTs representing the same object.