NFT stands for non-fungible token. This means a token or coin that cannot be interchanged, copied, replaced or subdivided. Unlike fungible tokens which can be swapped, non-fungible tokens are only available in its indivisible original form; they cannot be directly replaced with another digital asset.

An example of a fungible asset is physical currency. A $20 note can be exchanged with ten $5 notes, they are the same amount so the exchange is valid but a person's name and DNA cannot be replaced with another person's name and DNA because the DNA is unique to only the owner of it; that is just the whole idea with NFTs. They cannot be exchanged or swapped for other NFTs as if they were crypto coins because NFTs have their own unique features and identifiers which sets their values apart from every other NFT.

It is for this reason that NFTs have become really popular with intellectual property and copyright owners seeking to keep their works original and unadulterated.  How did NFTs come to be what they are today? They literally were unknown a few years back to be having this much hype they get now.