Per dictionary definition, fungible means ‘replaceable by another item.’ Essentially, with fungible items, it doesn’t matter which exact item is offered since they all have the same value. A great example of fungible assets is money. $100 would always be $100 regardless of the specific note. Thus, if an item is worth $100, anyone can exchange any $100 note for that item. In the same vein, cryptocurrencies are fungible. This means that nobody really pays attention to the exact bitcoin they own because all bitcoins have the same value.
However, NFTs are different. They are not equal to one another since each has a unique digital signature. The value of a specific NFT is determined by the underlying asset it represents. Thus, while one NFT might be worth $500, another may sell for millions.