Identifier for an app that is unique across all apps within a given platform
Many platforms require consuming apps to identify themselves, so that the platform can decide which services can be provided to the app, how they should be provided, and at what rate. To that end, platforms often require developers to identify a list of apps which will use the platform, and the platform issues each one with an identifier string. The identifier string is unique across all apps which may use the platform and is typically a long, random, string (a "GUID").
