Every cryptocurrency transaction must be added to the blockchain, the official public ledger of all completed transactions, in order to be considered a successful and valid transfer. The work of validating transactions and adding them to the blockchain is done by miners, which are powerful computers that make up a portion of the network and confirm its transactions. Miners spend vast amounts of computing power and energy doing this for a financial reward: with every block (a collection of transactions) added to the blockchain comes a bounty called a block reward, as well as all fees sent with the transactions that were confirmed and included in the block. For this reason, miners have a financial incentive to prioritize the validation of transactions that include a higher fee. For someone looking to send funds and get a quick confirmation, the appropriate fee to include depends on the cryptocurrency being sent and can vary greatly, depending on a number of factors, such as transaction size and network conditions.