Virtualization is one of most important elements that makes Cloud computing. Virtualization is a technology to helping IT organizations optimize their application performance in a cost-effective manner, but it can also present its share of application delivery challenges that cause some security risks. Most of the current interest in virtualization revolves around virtual servers in part because virtualizing servers can result in significant cost savings. The phrase VM refers to a software computer that, like a physical computer, runs an operating system and applications.