Fungibility is related to the interchangeability of specific goods. For example, you can exchange 1 dollar with another 1 dollar or exchange same-value products. Whereas, non-fungible means distinguishable. You can better understand it with an example. Suppose you have a dollar bill and you got the signature of a celebrity or politician on it. Now it has become unique or distinguishable. Although the bill looks like some other dollar bills, it is more valuable than others now. So what is unique and distinguishable is called non-fungible. Non-fungible tokens are unique cryptographic tokens based on blockchain technology. They can't be tempered, exchanged, and hacked.