When Bitcoin was unleashed on the world, it filled a specific need. But it wasn’t long before people realized the technology behind Bitcoin—the blockchain—could do much more than record monetary transactions. That realization has lately blossomed into a dazzling and often bewildering array of startup companies, initiatives, corporate alliances, and research projects. Billions of dollars will hinge on what they come up with. So you should understand how blockchains work—and what could happen if they don’t.