A composite component is constructed out of other components. To create a composite component, you have to list the names of the member (constituent) components and then specify how the ports of the member components are connected to each other and to the external ports of the composite component. You also specify which parameters of the member components are to be visible, and therefore adjustable, in the block dialog box of the composite component.
In certain ways, this functionality is similar to creating a subsystem in a Simulink® block diagram, however there are important differences. Simscape™ language is a textual environment, and therefore you cannot “look under mask” and see a graphical representation of the underlying component connections. At the same time, the textual environment is a very powerful tool for modeling complex modular systems that consist of multiple interconnected member components.