NFT stands for "non-fungible token". The difference between NFT and conventional tokens is that each such token is unique and exclusive.
For example, there are over 100 million ETH tokens, each of which is a token and is no different from any other token of the same kind. But in NFT, each such token contains a unique value, such as a bull from TON Bulls, of which there may be 10,000 in total. Each bull is made from a random combination of background, face, clothing, and hairstyle, which makes it unique.