It's a joke about how Bitcoin works - it needs processing power to function thus the people who 'run' (as in run the program) of Bitcoin are rewarded with Bitcoin Note : Bitcoin assumes two different identities. Bitcoin is what you spend and what the miners are paid in, but it is also the name of the program. What the joke is saying is this guy bought a phone and has been mining enough Bitcoin using it to pay off his mortgage.. Note entirely accurate, the processing power required would likely destroy your phone before you made any money but still a witty joke