What is the London hard fork on the Ethereum blockchain?

The London hard fork on the Ethereum blockchain is an update that affects the transaction fee model, as well as the “difficulty bomb”. London implies that a standard fee is used instead of gas. If earlier users themselves set the gas price in the auction format and miners could give priority to the block with the highest commission, then after the update, all blocks will have a fixed commission. The update ensures the transition of the platform to the Proof of Stake mechanism.