Centralised crypto is a digital resource built to be used as a medium of exchange. Additional units may be created via mining. Any person may do this if they've access to a device. Mining uses a large amount of hours and electricity, though. A high-powered machine is also vital, to do this effectively. Conversely, Ripple is a centralised resource, which is unmineable. A limited supply of coins were generated by the organisation and this limit will never be exceeded.