# 1.4 Consensus mechanisms
A consensus mechanism is a fault-tolerant mechanism that is used in a blockchain to achieve the necessary agreement on a single state of the network among distributed nodes.
Consensus mechanisms are vital for any blockchain existence. Since every node can submit transactions to be added to the blockchain, it’s necessary that all transactions are constantly checked and nodes need to reach a consensus to decide which transaction must be included.
There are different ways to reach a consensus:
Proof Of Work (POW) is the first blockchain consensus mechanism and was first used by Bitcoin. It is better known as mining and the nodes are known as miners. Miners solve complex (but useless) mathematical puzzles which require a lot computational power. The first one to solve the puzzle gets to create a block and receives a reward for creating a block. It costs an insane amount of energy to perform these computations and therefore POW is not an earth friendly consensus mechanism.
Proof Of Stake (POS) is consensus mechanism where nodes have a vested interest in keeping the network maintained and the value of its coins high. POS has a randomized process to determine who gets to produce the next block. Nodes need to stake their tokens to become a validator node and their tokens are lock up (staked) for a certain period.
Commercio.network uses the Proof Of Stake (POS) consensus mechanism, you need 50.000 Commercio tokens to become a validator, and the minimum staking period is 21 days. If you wish to leave the validator group you need to UNBOND and after 21 day your Tokens will be free to move.