This document provides an overview of ITILv3 (Information Technology Infrastructure Library version 3). It discusses what ITIL is, the key differences between versions 1, 2, and 3. It then covers some of ITIL's key concepts like services, service levels, configuration management, and the service lifecycle. The service lifecycle consists of five stages: service strategy, service design, service transition, service operation, and continual service improvement. The document provides brief explanations of some of the processes within these stages, including service portfolio management, financial management, and capacity management.