The traditional GUID (a.k.a UUID Version 4) is fine and works really well for it's intended use. But its random nature is problematic in some scenarios that's why other UUID versions have been created ...

On SQL Server, when a Guid property is value-generated, we use the special SequentialGuidValueGenerator; but when a string property is value-generated, we fall back to the core ValueGeneratorSelector, ...

If you are asking “GUI-what?”, not to worry, you aren’t alone. A GUID is a Globally Unique Identifier that helps manage the relational data in the Common Data Service for Apps and SQL Server.