Centralised crypto-coins are a digital holding created to be used as an apparatus of trade. Additional crypto-coins can be added through mining. Everyone can do this if they've access to a device. Mining requires a great deal of hours and electricity, however. A fast computer is also required, to do this effectively. On the other hand, XRP is a centralised asset, which can't be mined. A finite number of units were made by the company and this amount will never be exceeded.