Consensus
The consensus mechanism describes the method to validate and authenticate values or transactions in a decentral way. As a result, there is no need to rely on a central authority. Accordingly, there are various consensus mechanisms to achieve this. The most popular consensus mechanisms are proof of work (PoW) and proof of stake (PoS). They differ in the selection of the node for validating the next block. The proof of work consensus includes a cryptographical math problem. The one who solves the task is selected to broadcast the transactions to the network. In comparison, the proof of stake consensus is based on the validators that hold the largest stakes analogous to a poker game. Thus, all participants are equal, and no one has the sole power to validate the transactions.
Bitcoin uses proof of work as a consensus mechanism. Since the number of miners is very high, the task is very complex and thus requires a high computing power for each peer [1].
[1] Heines, R. (2017): Blockchain Technology Applications: A Conceptual Framework from a Supply Chain Perspective