A network fee is a transaction fee paid to blockchain validators or miners to process and confirm transactions on a blockchain network. It serves as an incentive for network participants to secure and maintain the blockchain while preventing spam and congestion. The fee amount varies based on factors such as network demand, transaction size, and the specific blockchain protocol. In networks like Ethereum, fees are calculated using gas, while Bitcoin fees are based on transaction data size. Network fees ensure efficient transaction processing and help maintain the overall integrity of the blockchain.