This document provides an overview of virtualization. It discusses that virtualization allows separation of resources from physical hardware, providing a layer of abstraction. This allows more efficient utilization of infrastructure through techniques like server consolidation and containment. Virtualization can be applied at different levels, including hardware, operating system, and application levels. The document compares hosted and hypervisor virtualization architectures and their advantages. It outlines how virtualization addresses challenges around server consolidation, testing/development, business continuity, and desktop management. Overall virtualization transforms independent physical servers, storage, and networks into pooled computing resources for improved efficiency and flexibility.