Centralised crypto-coins are a code-based asset created to work as a medium of exchange. Additional coins may be created via mining. Everyone may participate if they've access to a device. Mining uses a large amount of time and electrical power, however. A fast computer is also needed, to do this profitably. However, XRP is a centralised resource, which is unmineable. A finite number of units were made by the company and this limit will never be added to.