ITIL (Information Technology Infrastructure Library) is a framework of best practices for IT service management. It provides guidelines for key processes and common frameworks to help organizations improve service quality and reduce costs. The five key philosophies of ITIL are: 1) Managing IT as a service business focused on customer needs, 2) Ensuring high quality of services through understanding customer requirements, 3) Taking a process-based approach to service delivery, 4) Measuring key performance indicators to manage and improve services, and 5) Being aware of costs to balance quality and efficiency.