Proof Work

"Mining requires substantial computing power and electricity because miners must solve a difficult trial-and-error puzzle before a block can be added. After one miner finds a solution, other miners verify the proof of work and check the block's transactions against the existing blockchain to ensure that the miner did not create counterfeit payments or spend funds it did not control. Because each block contains the previous block's hash, changing historical data would alter the entire subsequent chain and reveal the tampering."