Consensus, in the context of a distributed computing network, is a mechanism by which multiple physically separated participants can reach an agreement over something (e.g. to agree if a transaction is valid and which block to place the transaction in). Several Blockchains employ a variety of mechanisms to achieve consensus, and this article tries to break them down in as simple a language as possible.Before we start, it is important to understand that there are basically two types of consensus mechanisms.Probabilistic (Which assumes that if enough nodes agree, it is POSSIBLE that a transaction could be reverted, but not PROBABLE). An example of this is BitcoinFinalistic (Which CONFIRMS that the transaction is final and will NEVER be reverted). An example of this is Algorand.To visualize the different consensus mechanisms, let’s consider a simple transaction. Let’s assume the transaction is the statement “The sky is blue.” Let’s consider the Blockchain as a Book of truths, each page representing a block. The aim is for us to get “The sky is blue” written into the book of truths.Proof of Work (PoW)Bitcoin, Ethereum (For now), and several other mineable Blockchains prefer to use a mechanism called PoW to reach consensus. Let’s visualize how “The sky is blue” gets written into a PoW Book of truths.Imagine that the Book of Truth is placed in the town square. People come from far and wide with their truths written on pieces of paper hoping to get them written into the book. Some officials surround the book and offer to write new truths into it. Anyone can volunteer to be such an official (Permissionless chain), but there’s a catch:For each truth that is presented to them, the officials have to solve a complex mathematical puzzle before they can examine the pieces of paper with the truths. The…