NFT stands for Non-Fungible Token.
Basically, you can create NFT by using Smart Contract based on Blockchain. It means everything is store on a certain Blockchain. Any Blockchain that provides a Smart Contract feature will be able to generate an environment to create NFT.
An NFT would normally contain an image with special attributes. The attributes can be anything that text-based, like a passcode, characteristic of an item, a description, etc.
An NFT would last forever on a Blockchain with a unique ID, and each is differentiated by its ID. They might contain the same image and attribute, but the ID will be different. Every data is recorded on a block with created time (timestamp). As a result, it creates authenticity.