Data-Flow Diagram
also called DFD
A diagram of how data moves between processes, stores and external entities, with trust boundaries drawn on it.
Its distinguishing feature is that it follows the data rather than the calls. Four element types — external entities, processes, data stores, and flows between them — plus, crucially, dotted lines marking trust boundaries.
That last element is why it is the standard artefact for threat modelling: almost every interesting threat lives on a boundary crossing, so a diagram that draws the boundaries makes the analysis systematic rather than imaginative. Walk each crossing and ask what could be spoofed, tampered with, disclosed or denied there.
It is also the right diagram for privacy and residency questions, because it answers "where does personal data go, and which of those places is outside our jurisdiction" — a question a component diagram cannot answer at all.