What is a Service? ITIL defines a Service as “a means of delivering value to customers by facilitating outcomes customers want to achieve without  the ownership of specific costs and risks.”

In other words, when we do something for another party that gives them something they want or value, we’re providing a service. Generally  speaking, because our users want the benefits and value of email, storage, wireless networking, etc., but don’t want to take on the burden of managing those items themselves, we provide those things to them as a service.

We also find it useful to distinguish between client-facing services that allow end users to do their work and internal technical services that enable those services. We use the term IT Service to describe the client-facing services and IT Provider Service for the internal, technical services. Definitions and examples are as follows:

IT Service

A service that is directly consumed by the end user to do their work and is something they ask for and recognize. It has the additional characteristics:

• You don’t use this service to consume or procure another service (as you do with CAS or networking, e.g.).
• If you provide this service alone to the end user, they would be happy to use it on its own.
• It’s discrete enough that you want to measure it; and ideally would be governed by a Service Level Agreement (SLA).
• It sometimes called an “end to end” IT service.

IT Provider Service

A technical service or component that enables IT Services. A single Provider Service can support multiple IT Services. It has the additional characteristics:

• To the extent that end users consume them, they are used for the sake of an IT Service. For example, CAS and networking exist to enable other services.
• End users may use them, but only to access or enable an IT Service.
• It would ideally be managed by an Operational Level Agreement (OLA).

EXAMPLES

Under this classification, ClassesV2 and YaleConnect are considered IT Services. They meet the criteria described above:

• The services are directly consumed by users and enable them to do their work, whether they are students, faculty, staff, or researchers. Using ClassesV2 allows a student to submit work or a faculty member to post a course syllabus. The service directly enables them to do their work at Yale.
• Users can consume this service independently of other IT Services. So even if we have multiple email services (such as YaleConnect and EliApps), an end user can consume one service independently of the other.
• Even lacking a formal SLA, these services should have defined service levels for the end users.

CAS and networking, on the other hand, are IT Provider Services. They meet the criteria described above:

• End users do not ask to use CAS on its own; it only has value to them insofar as it enables their use of an IT Service. For example, logging in via CAS allows you to use the Box@Yale service.
• The operational details of an IT Provider Service are generally described in terms of its availability (and reliability, etc.) for other services that depend on it, making it suitable for an OLA.

RELATIONSHIP BETWEEN IT SERVICES AND IT PROVIDER SERVICES

Every IT Service relies on one or more IT Provider Services, and every IT Provider Service supports at least one IT Service. For example, ClassesV2 (an IT Service) relies on multiple IT Provider Services, including networking, CAS, a working endpoint device (computer, tablet, etc.), and the actual ClassesV2 Sakai application.

If any of these components are not working properly, the end user cannot consume the IT Service ClassesV2. As such, the IT Service is an aggregate of all the IT Provider Services necessary for someone to use that service, not just the application. This relationship is illustrated below.

A WORD ABOUT TERMINOLOGY

We had previously used the term “Business Service” or “IT Business Service” for what we are now referring to as an IT Service. This more inclusive term better captures the meaning. If you see or hear the old term (with the b-word) as we transition to the current terminology, know that we mean IT Service as described above.

This service classification scheme is consistent with our service management framework and built into our ServiceNow environment. The CMDB is our canonical list of all services and maps the relationships between them.

Eventually, we’ll have comprehensive mapping of relationships and dependencies all the way from an IT Service, its related IT Provider Services, the applications that support it, and the networking components, servers, etc. that make up the full service map. Not only will this give us a comprehensive view of dependencies and connections, it will make the ticketing process easier because CIs will be picked directly from the CMDB.

Source: http://its.yale.edu/news/itil-foundations-what-service