To understand ERC20 and ERC721 contract standards, first, let's look at the concept of fungibility. Fungibility is used to describe the property of an asset where individual units do not hold a special value and can be replaced with another unit of the asset. A good example of this a 10 dollar bill. If you have a 10 dollar bill and I have a 10 dollar bill, they both hold the same value, which is 10 dollars. The bill would not have a higher or lower value depending on who is the owner of the bill. The bills can replace each other very easily. Hence, a 10 dollar bill is a fungible asset. All currency is essentially fungible in nature.
Now, take the case of a different kind of asset. If both of us owned a 400-square foot apartment and yours was in New York City and mine in New Delhi, the monetary value of both the apartments...
