Cryptocurrency fees can be defined as money (usually in the form of one of the virtual currencies) that is paid as a on top of a transaction. The most common way to charge a fee is by taking a commission, i.e. some percentage from the amount of the transferred money. At the moment, a lot of transactions can be completed without any cryptocurrency fees unless the transaction includes a large amount of data. As miners function as the handler of transactions, they also receive commissions since each new block of the blockchain consists of their operations and, for example, a fee from Bitcoin as well. It is optional to require a commission, but any user that has found a block can include fees by their own choice. In the future, when the rewards for creating a new block will be reduced, miners will get most of their profit directly from the fees.