THE ITIL FRAMEWORK
ITIL is not a standard in the formal sense but a framework which is a source of good practice in service management. The standard for IT service management (ITSM) is ISO/IEC 20000, which is aligned with, but not dependent on, ITIL.
As a formal standard, ISO/IEC 20000 defines a set of requirements against
which an organisation can be independently audited and, if they satisfy those
requirements, can be certificated to that effect. The requirements focus on what must be achieved rather than how that is done. ITIL provides guidance about how different aspects of the solution can be developed.
The International Organization for Standardization (ISO) and The Cabinet Office, with the cooperation of the independent user group itSMF (the IT Service Management Forum), have publicly committed to keeping the standard and
the framework as aligned as possible. However, it has to be accepted that they serve different purposes and have their own development lifecycles so it is unlikely that they will ever be completely synchronised.