A blockchain is a distributed digital ledger that records transactions in a verifiable way without a central authority. The document discusses how blockchain technology can be applied to identity management for both people and devices/things in the context of the growing Internet of Things. It outlines several key benefits blockchains provide for identity such as self-sovereign identity control, persistence of data over time, and the ability to uniquely identify any entity or object. The future of identity management is moving towards a user-centric model enabled by blockchain technology.