What type of services are NOT directly used by the business but are required by the service provider to deliver customer facing services?

Business services are IT services that directly support business processes and are visible to and consumed by business units, which is the opposite of what the question describes.

Component services is not a recognized ITIL service category - components refer to individual infrastructure parts, not a named service type in the service portfolio.

Supporting services are defined in ITIL as services that are not directly used by the business but are required by the IT service provider as foundational components to deliver customer-facing services. Examples include monitoring platforms, directory services, and backup services that operate behind the scenes. They are distinct from business services because end-users never interact with them directly.

Customer services are those directly consumed by customers or end-users, making them the customer-facing layer rather than the internal supporting layer the question describes.