To get a better understanding of what a Non-Fungible Token is, it helps to take a look at the real world. A unique, irreplaceable token is, for example, a painting or a handmade piece of jewelry. The counterpart, a Fungible Token, would be a $10 bill, for example. A painting or piece of jewelry is unique and cannot be replaced or exchanged for an equivalent object; a $10 bill, on the other hand, has many equivalent counterparts, namely all other $10 bills in circulation.
Back to the digital world: Fungible Tokens are Bitcoins, for example, which can be exchanged for other Bitcoins of the same value. But what about memes, videos, pieces of music, and actual works of art in the virtual space? In theory, anyone could duplicate them in just a few clicks. The Non-Fungible Token evolved as a way to identify and trade the original.