Using Docker containers
Docker is generally used to create containers, which run your application as if in a headless virtual machine. In fact, on host operating systems that are not Linux-based, Docker effectively runs Linux in a virtual machine and runs your containers within that virtual machine. This is done transparently.
Note:
You don't have to install VirtualBox yourself. Docker is packaged in such a way that it will install or use any already-existing virtualization technology (for example, a hypervisor) for your operating system.
Introduction to containers
Earlier versions of Docker installed VirtualBox to create its virtual machine, but more recent virtualization technology implemented within the operating systems allows Docker to use those technologies instead.
Docker for Linux containers expects the host operating system or the virtual machine to be running Linux. The containers share the Linux kernel with the host. Docker can be used to run Windows...