Bitcoin is an online communication protocol that facilitates virtual currency including electronic payments. Since its inception in 2009 by an anonymous group of developers, Bitcoin has served tens of millions of transactions with total dollar value in the billions. Users have been drawn to Bitcoin for its decentralization, intentionally relying on no single server or set of servers to store transactions and also avoiding any single party that can ban certain participants or certain types of transactions. Bitcoin is of interest to economists in part for its potential to disrupt existing payment systems and perhaps monetary systems, and also for the wealth of data it provides about agents' behavior and about the Bitcoin system itself. This article presents the platform's design principles and properties for a non-technical audience, reviews its past, present and future uses, and points out risks and regulatory issues as Bitcoin interacts with the conventional financial system and the real economy.