Virtualization was a breakthrough innovation that completely changed the way physical servers were looked at. It refers to the abstraction of a physical object into a logical object.
Virtualization of physical servers enabled the creation of multiple virtual servers, better known as virtual machines. These virtual machines consume and share the same physical CPU, memory, storage, and other hardware with the physical server on which they were hosted. This enabled faster and easier provisioning of application environments on demand, providing high availability and scalability with reduced cost. One physical server was enough to host multiple virtual machines, each virtual machine containing its own operating system and hosting services on it.
There was no longer any need to buy additional physical servers for deploying new applications and services. The existing physical servers were sufficient to host more virtual machines. Furthermore, as part of rationalization, many physical servers were consolidated into a few with the help of virtualization.
Each virtual machine contains the entire operating system and each virtual machine is completely isolated from other virtual machines, including the physical hosts. Although a virtual machine uses the hardware provided by the host physical server, it has full control over its assigned resources and its environment. These virtual machines can be hosted on a network such as a physical server with its own identity.
Azure helps in creating Linux and Windows virtual machines in a few minutes. Microsoft provides its own images along with images from partners and the community. Users can bring in their own images. Virtual machines are created using these images.