NFT stands for Non Fungible Token. While I don´t love the name that is the accepted standard term right now. It refers to one off non-divisable tokens. Maybe you heard about Homerpepe that sold for over 30k usd in pepecash, that is a pre-NFT NFT , meaning that it was an NFT before the term even existed and before there was a hype around the term.
They can be useful for one off artwork, trading cards, or anything that is unique like a fingerprint. If you wanted to give someone a sea shell as people do on the island Malaita then it would be one of a kind and this could be represented digitaly in the form of a Non Fungible Token.