Information Technology Infrastructure Library (ITIL) is a set of concepts and techniques for managing information technology (IT) infrastructure, development, and operations.

ITIL is published in a series of books, each of which cover an IT management topic. The names ITIL and IT Infrastructure Library are registered trademarks of the United Kingdom's Office of Government Commerce (OGC). ITIL gives a detailed description of a number of important IT practices with comprehensive checklists, tasks and procedures that can be tailored to any IT organization.

ITIL v3, published in May 2007, comprises 5 key volumes:

1. Service Strategy

2. Service Design

3. Service Transition

4. Service Operation

5. Continual Service Improvement

Service Strategy

Service strategy is shown at the core of the ITIL v3.1 lifecycle but cannot exist in isolation to the other parts of the IT structure. It encompasses a framework to build best practice in developing a long term service strategy. It covers many topics including: general strategy, competition and market space, service provider types, service management as a strategic asset, organization design and development, key process activities, financial management, service portfolio management, demand management, and key roles and responsibilities of staff engaging in service strategy.

Service Design

The design of IT services conforming to best practice, and including design of architecture, processes, policies, documentation, and allowing for future business requirements. This also encompasses topics such as Service Design Package (SDP), Service catalog management, Service Level management, designing for capacity management, IT service continuity, Information Security, supplier management, and key roles and responsibilities for staff engaging in service design.

Service Transition

Service transition relates to the delivery of services required by the business into live\operational use, and often encompasses the "project" side of IT rather than "BAU" (Business As Usual). This area also covers topics such as managing changes to the "BAU" environment. Topics include Service Asset and Configuration Management, Transition Planning and Support, Release and deployment management, Change Management, Knowledge Management, as well as the key roles of staff engaging in Service Transition.

Service Operation

Best practice for achieving the delivery of agreed levels of services both to end-users and the customers (where "customers" refer to those individuals who pay for the service and negotiate the SLAs). Service Operations is the part of the lifecycle where the services and value is actually directly delivered. Also the monitoring of problems and balance between service reliability and cost etc are considered. Topics include balancing conflicting goals (e.g. reliability v cost etc), Event management, incident management, problem management, event fulfillment, asset management, service desk, technical and application management, as well as key roles and responsibilities for staff engaging in Service Operation.....

Continual Service Improvement (CSI)

Aligning and realigning IT services to changing business needs (because standstill implies decline).

The goal of Continual Service Improvement is to align and realign IT Services to changing business needs by identifying and implementing improvements to the IT services that support the Business Processes. The perspective of CSI on improvement is the business perspective of service quality, even though CSI aims to improve process effectiveness, efficiency and cost effectiveness of the IT processes through the whole lifecycle. In order to manage improvement, CSI should clearly define what should be controlled and measured.

CSI needs to be treated just like any other service practice. There needs to be upfront planning, training and awareness, ongoing scheduling, roles created, ownership assigned,and activities identified in order to be successful. CSI must be planned and scheduled as process with defined activities, inputs, outputs, roles and reporting.