A Component Diagram is a visual representation of the components and their relationships within a system. It is used to show how the components interact with each other and how they are organized. The diagram can also be used to identify potential areas of improvement and to help with the design of new systems.
From Wikipedia
In Unified Modeling Language (UML), a component diagram depicts how components are wired together to form larger components or software systems. They are used to illustrate the structure of arbitrarily complex systems.