Centralised crypto-coins are a digital asset created to work as an item of exchange. New units can be created by mining. Any person can participate if they've access to a computer. Mining requires a lot of hours and electrical power, though. A fast computer is also required, to mine successfully. On the other hand, Ripple is a centralised resource, which is unmineable. A fixed number of coins were generated by the organisation and this amount will not be exceeded.