Consensus mechanisms are necessary to confirm the correctness of transactions in blockchain networks. The main types of consensus are proof of work (PoW) and proof of stake (PoS). In PoW, network nodes (miners) solve complex mathematical problems to confirm transactions and add new blocks. In PoS, network participants (validators) confirm transactions and create new blocks based on the amount of cryptocurrency they own and are willing to stake. These mechanisms ensure the security and integrity of data in blockchain networks.