Keystone is the OpenStack identity service that handles authentication and authorization. It implements the OpenStack Identity API and acts as a broker between OpenStack and other identity services, as well as providing discovery services. Key components include the keystone service itself as well as related middleware, clients, and libraries. Key concepts handled by Keystone include users, groups, roles, assignments, policies, tokens, and the service catalog. Ongoing initiatives focus on areas like system scope, read-only roles, unified limits, application credentials, federation, edge support, testing, and documentation.