I’ll simplify it the best I can:
If you wanted to buy or sell a piece of artwork or music online without using cash which is fungible, you could sell it with Bitcoin or ETH.
Now, how do you know what you’re buying is real? Because there’s a digital signature of this particular asset that is only specific to the seller/buyer that cannot be replicated; it’s like an insignia & within this insignia is the verification that what you’re buying/selling is 100% yours. That’s a NFT.
So as a way to maintain the value of the asset without it being devalued by the exchange you use a NFT as a placeholder for the currency value of the asset. Meaning, you use a Non-Fungible Token to either buy or purchase the product with Bitcoin & can continue to benefit on the value of the asset after the sell or purchase because you didn’t exchange it for a fungible token a.k.a cash.
Paintings & music lose their value once they’re bought & sold, the way to keep & increase the value of it is to sell it or buy it without using an fungible exchange; so if someone buys a Million dollar Da Vinci painting it’s not worth that anymore & can’t be resold at a higher price, but if someone buys a Digital piece from Banksy it can be resold at a higher price because it didn’t lose it’s value because it wasn’t exchanged for cash or credit, but rather a digital cryptocurrency with an NFT.
It’s just a way to sell & buy art, music, videos & other digital assets online without it losing it’s value & knowing that it isn’t a forgery.