Virtualization
A virtualized environment abstracts the concept of a physical machine, running on top of a physical (or virtual) machine.
According to the Wikipedia, virtualization is described as:
virtualization: refers to the act of creating a virtual (rather than actual) version of something, including virtual computer hardware platforms, storage devices, and computer network resources.
When it comes to the deployment of applications, the strategy followed for metal deployments can also apply on virtualized environments, but other kind of deployments arised as well: start a machine from a given template (or snapshot), including the application, or a mixed approach in which certain components and pre-requisites come with the template or snapshot, and some automation is used to deploy the desired version of the application.
Since booting virtual machines is to all effects booting a machine with a fully fledged operating system the startup time is still in the orders of metal deployments.
Or, virtualized infrastructure can also virtualize other machines, where we can run our application onto. This is referred as nested virtualization: