# So, how do Meta Mask coordinate all that?

As mentioned previously, an essential function of a blockchain network is coordinating the process of agreement between all the nodes in the network regarding whether a transaction is valid or not. The agreement is referred to as *consensus*, and the process by which it occurs is called a ***consensus mechanism**,* or *consensus protocol*. Ethereum has used two different consensus mechanisms at different points, the first being **Proof of Work (PoW)** and the second, **Proof of Stake (PoS)**. In both mechanisms, computers are provided to do the work of verifying the validity of the transactions, and agreeing on them.

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