Hello,

InteractionUse is one of UML2 models.

An InteractionUse refers to an Interaction. The InteractionUse is a shorthand for copying the contents of the referred Interaction where the InteractionUse is. To be accurate the copying must take into account substituting parameteres with arguments and connect the formal gates with the actual ones.
It is common to want to share portions of an interaction between several other interactions. An InteractionUse allows multiple interactions to reference an interaction that represents a common portion of their specification.

For details please refer to P.473 of the Unified Modeling Language: Superstructure version 2.0 published by OMG.

To see the image of CombinedFragment, please check at UML 2.0 Models in Sequence Diagram.

Best regards,
Satomi