NFT is an acronym for Non-Fungible Token.
An NFT is a way to prove ownership or usage writes of either a digital or a physical asset. It can be artwork, Music, a movie, access to a venue or concert or many other things.
Every NFT is completely unique hence Non-Fungible or not fake able. If it is a piece of art, it may have others in the series that look the same, but every one will have a unique number assigned to it making it 100% unique.
With NFT artwork, while you can click on the image and see it, and even save it or make a copy of it. It is not yours, and you do not have ownership or the rights to use it personally or commercially unless you own the NFT.