Centralised crypto-coins are a digital asset designed to be used as an apparatus of exchange. Additional units are added by mining. Any person is able to do this if they've access to a computer. Mining uses a lot of hours and electricity, though. A high-powered machine is also vital, to mine profitably. However, XRP is a centralised resource, which cannot be mined. A finite supply of coins were created by the company and this limit will not be exceeded.