A variable number to which set fees needs to be multiplied by, to give an adjusted fee amount to be paid for transactions. Operators of registered nodes on the network may take a regular vote on the appropriate multiplier, which we call the fee scale, for minimum transaction fees. This guarantees that while the value of the blockchain token may fluctuate, the fees to be paid for transaction remain stable against regular currency.
Fungible means that a given good is identical (a.k.a., interchangeable). In crypto, we often talk about fungible or non-fungible tokens. A fungible token is Bitcoin. One Bitcoin is and will always be one Bitcoin, just like any other Bitcoin.