Components can be containers for networks of nodes, like sub-patches. A component has Inputs and Outputs and Parameters to control whats happening on the inside – just like an operator.
Right-click on the network path to see the option menue for the component in which you currently are. You can access the Customize Component option and the Parent Parameters from there.
Components can be stored external in their own fileformat .tox and quickly accessed through the palette browser. When you plan a TD network, you should try to break up the process into smaller bits – components, that in the best case should be working on their own and that talk to each other. This way you can reuse them or collaborate with other programmers. Nested components are also the way to structure bigger networks.