A metamodel diagram describing the structure of a SysML/UML Model.
Package diagrams are high-level Namespace containers. They section off parts of the SysML or UML model which they’re a part of. There is no one ‘correct’ way to organize a model, therefore package diagrams help communicate whatever means was chosen. The represent containment, and can represent nested packages for greater levels of organizational fidelity.
They’re also boring.