ITIL® may bring a structured, easy-to-understand and easy-to-implement framework, but it also uses clearly defined terminology that enables ITIL experts around the world to understand each other. As in any other field of interest, ITIL terminology also uses terms that may differ from their usual meanings in the English language, while others may be self explanatory.

Within this article, some common, and important, ITIL terms will be explained.


What better way to start with ITIL terminology, than with an explanation of service. Service is anything that you have to do, in order to make deliverables valuable to the customer. For example, e-mail as a service is what customers will use to exchange messages, files, documents, etc. However, the customer will not be aware of, or interested in, the technology behind it, or how it’s set up, as long as it can be used reliably – it’s considered valuable. You can read more about IT Service Management here.

Service Catalog and Service Portfolio

Often, there is confusion between Service Catalogue and Service Portfolio, as both contain lists of services and corresponding SLAs. However, while Service Catalogue contains only a list of active services that are available to the customers, Service Portfolio contains a list of all services: active, active but not available (e.g. legacy systems that are still used by few end users), services in development or planning, and services that have been shut down.

Service Level Agreement (SLA) and Operational Level Agreement (OLA)

Service Level Agreement is document signed between customer and service provider in which service and guaranteed levels of service delivery are described. For example, a SLA would include the time frame in which service will be available, metrics that will be measured in order to provide the expected level of service, etc. Operational Level Agreement, on the other hand, is an agreement between organizational teams that are included in service delivery. There might be several teams involved in service delivery (server, networking, application…), which all must work together in order to meet the requirements stated in the SLA.

Utility and Warranty

Utility and Warranty are like two sides of the same coin, and without them service has no meaning. Utility is commonly referred to as “fit for purpose,” and Warranty as “fit for use.” You can imagine Utility as a service’s ability to do what it was built to do (e.g. an e-mail service must be able to send and receive e-mails). Warranty, on the other hand, is a service’s ability to be usable by the customer in the expected and agreed way. For example, if you have an e-mail service that is used for sending and receiving e-mails (Utility), but it can’t handle more than two concurrent emails, or every 100th email gets lost, than that service’s Warranty is failing.

Incident, Problem and Known Error

An Incident is an event that caused degradation or disruption of a service (e.g. e-mail is not working). Read more about ITIL Incident Management.

A Problem, on the other hand, is the root cause of the incident, or many incidents that repeat with the same root cause (e.g. e-mail is not working, file sharing is not working, users can’t print, all due to a network outage – all at the same time, generating lots of related incidents). A good example of the difference between ITIL’s definitions of Incident and Problem are the famous words from Apollo 13: “Houston, we have a problem.” However, according to ITIL, the correct terminology would be “Houston, we have an incident.”

A Known Error is an incident or a problem whose root cause has been identified and some sort of Workaround has been implemented. It will remain a known error until change is applied that will correct the root cause permanently, and then it is referred to as a Solution.

Service Desk

Service Desk is a single point of contact between end users and service provider. It’s used to receive and resolve incidents, service requests, requests for information, and to communicate and coordinate communication, between service provider and end users (customers). However, people commonly think of Call Center, Help Desk and Service Desk as synonyms, which is not the case – as a Call Center doesn’t attempt to solve incidents, and a Help Desk doesn’t handle service requests. More information about Service Desk is available on this blog post: Service Desk: Single point of contact.

Service Request

Service Request is another ITIL term, which is used for requests for new services or alteration of existing ones. For example, an end user may ask for internet access (new service), or increase of mailbox size (alteration). In general, Request For Information is considered to be part of Service Request, and so is Request For Change.

Request for Change

Change Management is an important part of ITIL and IT Service Management in general; therefore, any change needs to start with a formal and detailed request to make the change – Request for Change (RFC). The RFC has to include a description of the change, whether there is a business need behind it, components / services that will be affected, cost estimates, risk assessment, and approval status. Get more information about ITIL V3 Change Management – at the heart of Service Management.

An example would be installation of a new application server that is required by the finance department. According to ITIL best practice, you can’t just go and purchase a new server, install some software and attach it to the corporate network. There might be not enough room in the data center racks, or not enough power supply or cooling, or there might be an unused server already available. These and numerous other reasons must be considered before implementing, but most important is that there is clear trail in the form of formal requests that will then start the change process.