Transaction fees are charges that are applied when a financial transaction occurs, such as buying or selling goods, transferring money, or trading assets. These fees can vary based on the payment method, the service provider, and the type of transaction. For example, using a credit card may incur higher fees compared to a bank transfer. In the context of cryptocurrencies, transaction fees are paid to miners or validators for processing and confirming transactions on the blockchain. These fees help maintain the network's security and efficiency, as they incentivize participants to validate and record transactions accurately.