Flash-mintable tokens (FMTs) allow flash minting -- the ability for anyone to mint an arbitrary amount of tokens into their wallet, as long as they also burn the same amount of tokens before the end of the transaction. You can think of FMTs as "credit tokens." Flash-minting is like "running up a tab," and burning the tokens at the end of the transaction is equal to "paying off your tab." If you don't "pay off your tab" before the end of the transaction, the transaction is reverted.