"Transaction fees" or "mining fees" represent the compensation for "miners", who play a vital role in the operation of cryptocurrencies. These individuals or groups utilize significant computational power to validate and record transactions on the blockchain, ensuring the network's security and stability.
These fees are not arbitrary: they serve as an incentive for miners to process and validate your transaction, especially during times of network congestion. The higher the fee, the more likely your transaction will be processed quickly. They, therefore, fluctuate based on demand, the complexity of the transaction, and network congestion.
It's important to note that these fees do not go to the platform or service you are using but are directly received by the miners once the transaction is confirmed. It's this incentive system that allows decentralized blockchains, like Bitcoin or Ethereum, to operate securely and autonomously.