 Down the rabbit hole is a segment where I answer a question that I ask myself. Andreas, hey, what is an NFT? I'd like to tell you that NFT means naming failure total. Because the term NFT is one of those things that is very difficult to explain and very poorly named. An NFT is a type of deed. The acronym NFT means non-fungible token, which is what I like to call a negative explanation. You ask me, what is an NFT? I give you an answer and now you have two questions because now you don't know what non-fungible token means. I have to explain that and also what fungible means. Fungible means that any unit of, say, a currency is indistinguishable from every other unit of a currency. If you give me a dollar bill, I don't care if the serial number ends in a two or three or five. It's still just a dollar bill. That is a fungible currency. It is fungible by law. If, however, I give you the title and registration of my current vehicle, then you will say, hey, can I use this to claim ownership to any vehicle? No. You can only claim ownership to the Toyota Corolla that I am currently driving. The specific one with this registration number, that is a deed. It's a title of ownership. It is non-fungible because it does not represent any possible variation of that type of item. It represents a specific instance, not any Toyota Corolla, not any car, this car. And so that is what a non-fungible token is. It is a token that represents a unique item. Now, it can be a physical item, for example, a house, a boat, a car, or it can be an intangible item, for example, a picture or the intellectual property of my logo or something else. And that may have some degree of recognition by some authority or none at all. For a digital item, you can prove ownership with a blockchain and the digital item itself may give you some kind of special privileges. Now, let's say, for example, you have a non-fungible token that is related to a piece of art, a digital photo. Can someone copy the photo? Of course they can, just like they can photocopy a signed copy of my book. But it's still not the original signed copy of my book that I signed. They can't copy the non-fungible token that proves that it was issued by me, for example, and therefore that's what they own. They don't own the digital image because that can be copied. They own the proof that I issued it, which gives them bragging rights. It gives them the ability to say that they are a patron of my work. It gives them the ability to say that they have recorded a unique moment. And that may have meaning or value depending on how you look at this space. It's very often easy to be cynical about these things and not see why these things might have value. But I think they do. I think that they can have meaning for those who collect these things. Ultimately, that's what they are, collectibles. But they're programmable collectibles that have special features. For example, let's say I gave out a signed copy of my book as an NFT and you have the e-book. Well, you can copy the e-book. In fact, it's open licensed, but the NFT proves that you got it from me as the author and that's the same as me putting an autograph in it. But it doesn't end there. I could make it so that presenting ownership of that NFT, for example, with a digital signature from the same key that owns the NFT, you could gain access to the secret super-duper exclusive member's only area on my website where you could ask me questions. I wouldn't do that, but that's something you could do with an NFT. So you can use it as an access token. Maybe I go and do a concert at Madison Square Garden where I talk about NFTs and then you can use your ownership of the NFT as a ticket to come and see me. Madison Square Garden, call me if you want to book this. I'll be available. And then you could also use it to do something in the real world. For example, if I represented the title and registration of my Toyota Corolla with an NFT, maybe the NFT could sign a message that starts that car. So effectively, it's also the key. It opens the door and allows you to drive away. So if I transfer ownership of the NFT to you, you can now use that as a digital key to start the car and drive away. So ownership and control over the asset becomes one and the same. And there are many other things. I could also do things like deliver a stream of royalty revenues, dividends, or royalty payments to my audience. So these things are very flexible. They allow us to do things with tokens. And the real, the only characteristic that makes something an NFT is the fact that it represents a unique item of any tangible or intangible form and its ownership can be verified on a blockchain, can be transferred on a blockchain and you can build secondary markets and various programmable features. Other than that, it's a token and anything you can do with tokens, you can do with non-fungible tokens, but they have some very unique properties because they are non-fungible. Can NFTs expire? If you want them to, they don't expire at the moment, but you could implement a kind of enhanced NFT standard that has some additional features including expiry. Let's think about this for a second. What is an NFT? Very much like an ERC-20 token, an NFT, which if I remember correctly is a ERC-721. I don't remember the number by heart. That type of token specification specifies the minimum interface available for a token to be compatible with the standard. So it has to support, let's say, five different calls that allow you to do certain things with that token. The code base of an NFT or an ERC-20 token doesn't have to only restrict itself to the five function calls that are defined in the ERC specification. It has to have those so that other applications, exchanges, etc., can interact with these things in a way that is standardized and compatible with all of the available wallets. But you could do more. And many tokens do more things. They have additional capabilities, features, or even limitations, constraints that are implemented in code and with function calls that are outside or extensions of the standard. And those may be further standardized with additional standards or not. They may be custom to a specific NFT. So you could write an NFT that has some additional functions that do things like expiry. And you could implement those functions so that each NFT also has an additional field, which is maybe its expiration date. And then you could check if it's expired or not. And you could limit how the other functions work. So yes, you can do that. That's the interesting thing about programmable smart contracts. Hi, thanks for watching the video. I'm Andreas Antonopoulos. I'm the author of Mastering Bitcoin, Mastering Ethereum, and the Internet of Money series. If you'd like to support my mission of bringing education about Bitcoin and open blockchains to as many people as possible under open free Creative Commons licenses, please consider subscribing to my channel and supporting me on patreon.com slash A-A-N-T-O-N-O-P. Thank you.