In this sense, “subcomponent” refers to a relationship between components. It is not a distinct item in itself.
If you navigate to a component’s page, you can see all components it is a subcomponent of by navigating to the Found in components section.
If a component does not have this section on their page, then they are not a subcomponent of any component.
You can see all subcomponents a component has by looking at the Subcomponents section of a component’s page.
If a component does not have this section, then they do not have any subcomponents.