There is no central authority such as a clearing house or central banks to approve transactions as happens in our traditional daily transactions. In Bitcoin transactions, the technology underlying it called Blockchain uses distributed consensus where multiple computers or nodes approve these transactions based on mathematical calculations. All these nodes have to arrive at a consensus to approve or reject the transaction. The term distributed consensus indicates the fact and the way in which the nodes in a blockchain synchronize their data and reach a consensus regarding transactions happening i.e. Alice received 3 bitcoins from Bob. Since the majority of the nodes should reach a consensus before updating the distributed ledger the consensus they reach is called distributed.