What is Fungible Token
A fungible token is a token whose fundamental unit or attributes is interchangeable with other tokens of the same set. Put differently, fungible tokens are not unique. Examples of fungible tokens are Monero, Decentralandís MANA or Ethereumís Ether.
Fungible tokens are NOT unique, distinguishable digital assets or tracable. Any token will do the job or can be swapped for any other of that token.
Gold, silver, coins and bank notes is fungible since a specified amount of one is equivalent to that same amount of another. E.g. one ounce gold coin is and can be used the same as any other one ounce gold coin without regard from where it come from or mined if the contract is for one ounce gold coin.