Normal cryptocurrency is a code-based holding built to be used as an item of trade. New crypto-coins can be added via mining. Anyone can do this if they've access to a device. Mining requires a large amount of time and electricity, however. A fast machine is also required, to mine profitably. Conversely, XRP is a centralised resource, which is unmineable. A limited amount of units were created by the company and this limit will never be exceeded.