Centralised crypto-coins are a code-based holding created to be used as an apparatus of trade. New units can be found by mining. Any person is able to do this if they have a a computer. Mining requires a great deal of time and electrical power, however. A fast computer is also needed, to do this successfully. However, XRP is a centralised resource, which can't be mined. A limited supply of units were created by the company and this amount will never be exceeded.