Many components have dependencies on other components. The installer provides logic to ensure that those dependencies are met. For this reason, When you select a component to install, the installer automatically includes the components and subcomponents upon which the selected component has dependencies.
You cannot deselect a component if another selected component depends upon that component locally. However, if the dependency is not local, you receive a warning but are able to proceed under the assumption that the dependency is satisfied by a component on a different host computer.