One of the main reasons that most businesses like virtualization is to save money. Of course helping the budget is a good idea, but there are additional reasons to virtualize and different levels of virtualization as well.
After listing reasons for virtualizing, there is a section on the early origins of virtualization and how some of the ideas introduced in the beginning of virtualization are still prevalent today. Although server virtualization gets most of the attention, there are other types of virtualization available.
The conclusion lists different types of virtualization in IT, including naming some of the major vendors in each area.