Consensus Mechanism
The rulebook by which thousands of independent computers agree on one version of the ledger without a referee.
A consensus mechanism is how a decentralized network agrees on which transactions are valid and in what order — without any central referee. The two dominant designs are Proof of Work (Bitcoin: security through expended energy) and Proof of Stake (Ethereum since 2022: security through economically at-risk collateral).
Every consensus design trades between security, decentralization and speed — the so-called blockchain trilemma. When evaluating a chain that advertises huge transaction throughput, the first question is what consensus compromise paid for it: fewer validators, trusted committees, or weaker finality guarantees.