“Fungible” means an item is interchangeable with another item. For example, a one dollar note can be replaced with another one dollar note. They are essentially the same thing and if you swapped one with a friend, neither of you would lose or gain anything.
“Non-fungible” means two items are not interchangeable. They have attributes that make them unique. For example, one house isn’t interchangeable with another house. One house might be a mansion, another might be a shack. They are different items, even if they are both classed as houses, but if you swapped a house with a friend, one of you might gain and the other may lose due to the difference in attributes.
Meanwhile, a token is something that represents value. For example, a gift-card is a token. The gift-card is just a piece of plastic that doesn’t have any value, but it represents value and can be exchanged for that value.
So, a NFT is something that represents value and exhibits non-replaceable characteristics. A NFT could take the form of a digital token that represent a collectible piece of digital art.