Centralisation refers to the control of any activity being centralised - or under a single authority. In the case of currencies it means that the central bank controls everything for that nation's currency. This includes decisions such as increasing or decreasing its supply. Such currencies are also physically available in bills and coins. As a result, while this type of currency is still popular and widely used, one needs to appreciate how far decentralised currency, like cryptocurrencies have come over the past few years. Decentralised currencies like crypto involve lower fees, faster settlements and they are secure.