Consensus

Consensus is the process by which the many independent computers in a blockchain network agree on a single, shared version of the ledger without a central authority. Consensus rules define which blocks and transactions are valid and how the next block is chosen, so honest participants converge on the same history even when some act badly or go offline.

Proof of work and proof of stake are two common mechanisms. A common misconception is that consensus means everyone votes on each transaction; instead, participants follow shared rules that make one valid history the version they all accept.