In Unified Modeling Language (UML) diagrams, an interaction frame provides a context or boundary to the diagram in which you create diagram elements, such as lifelines or messages, and in which you observe behavior.
As the following figure illustrates, an interaction frame is displayed as a rectangular area with a heading label, or pentagon descriptor figure, in the top left corner.
The frame and its contents represent an interaction in a sequence diagram. The heading label of the interaction frame is the name of the interaction that the diagram represents.