An NFT (non-fungible token) is a token that's unique and not interchangeable with another token of the same kind — unlike a coin, where any one unit is identical in value to any other. NFTs are commonly used to represent ownership of digital art, collectibles, or increasingly, claims on other assets or access rights.
It's important to understand exactly what an NFT verifies: typically, that you own a specific token on the blockchain, which may (or may not) have reliable rights attached to the thing it's meant to represent. The token and the underlying asset it claims to represent are two separate things worth verifying independently.