ITIL (Information Technology Infrastructure Library) is a framework of best practices for managing and delivering IT services. It is designed to help organisations improve the quality and efficiency of their IT services, and align them with the needs and expectations of their customers. ITIL is used by many organisations around the world to guide the design, delivery, and support of their IT services.

The ITIL framework is divided into five main categories, known as the “ITIL Service Lifecycle”:

1. Service Strategy: This category focuses on defining the overall strategy and direction for IT services. It includes processes for identifying and evaluating potential services, as well as developing and implementing service portfolios.
2. Service Design: This category focuses on designing and developing new IT services, or modifying existing ones. It includes processes for creating service-level agreements (SLAs), service design packages (SDPs), and other design documents.
3. Service Transition: This category focuses on transitioning new or modified IT services into production. It includes processes for testing, deploying, and releasing new services, as well as managing the change process.
4. Service Operation: This category focuses on the day-to-day operation of IT services. It includes processes for managing incidents, problems, and requests, as well as monitoring and controlling the performance and availability of IT services.
5. Continual Service Improvement: This category focuses on continuously improving the efficiency and effectiveness of IT services. It includes processes for measuring and analysing service performance, identifying opportunities for improvement, and implementing changes to improve service quality.

ITIL provides a comprehensive set of best practices and guidelines for managing and delivering IT services, and is widely recognised as a leading framework in the IT industry. By following the principles and practices of ITIL, organisations can improve the quality and efficiency of their IT services, and better meet the needs of their customers.