GlobalID provides a unique identifier for model objects across all classes in an application. It consists of the application name and a class-specific identifier. GlobalID can be used to reference different object types using a single identifier, for job scheduling, and for dropdown lists. When used with ActiveJob, GlobalID serializes and deserializes arguments by converting them to and from strings. Internally, GlobalID uses the URI class to parse the identifier into its constituent parts like host, path, and scheme.