In the context of blockchain and cryptocurrencies, consensus refers to the process of coming to an understanding among network members regarding the legitimacy of transactions and the current state of the distributed ledger. The integrity and security of the blockchain depend on this agreement.
Without relying on a centralized authority, consensus mechanisms such as Proof of Work (PoW) or Proof of Stake (PoS) are used to validate transactions and come to a consensus on the state of the network.