ITSM concepts are often described in the context of only one of these type. Type I, type II and type III

Service Units is not an ITIL-defined term used for the Type I, II, III classification framework.

Business Units are the consumers or clients of services in ITIL and are not classified into Type I, II, or III categories.

In ITIL, Service Providers are the entities classified into three types: Type I (internal service provider embedded within a business unit), Type II (shared services unit serving multiple business units), and Type III (external service provider serving external customers). This classification describes the structural and commercial relationship between the provider and its customers.

Customers are external stakeholders who receive value from services and are not the entities classified under the service provider type model.