Introduction
Figure 1
A conceptual representation of an ordinary
computer system. The operating system oversees the physical hardware
resources and is responsible for executing individual applications and
allocating those resources to them.
Figure 2
Normally, computers run a single operating system with a single set
of applications. Sometimes (for reasons we’ll discuss soon), people
might want to run a totally separate operating system with a different
set of applications. One way to do that is to split up the physical
resources like CPU, RAM, etc. and present them to that second operating
system for its exclusive use. The concept of splitting up these
resources (i.e., virtualizing them) so that only this second operating
system can access them is the idea behind a virtual machine. 
Figure 3
Containers are environments that encapsulate
applications and their dependencies. Applications running inside a
container are functionally isolated from the host. The container manager
runs containers and determines what each container can “see” outside of
itself.
Virtual machines using VirtualBox
Figure 1
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