Centralised crypto-coins are a digital resource built to be used as an apparatus of exchange. Additional coins may be added through mining. Any person can participate if they have a a computer. Mining uses a lot of time and electrical power, however. A powerful machine is also vital, to do this effectively. On the other hand, XRP is a centralised coin, which can't be mined. A finite supply of tokens were created by the company and this limit will never be exceeded.