A container consists of an entire runtime environment: an application, plus all its dependencies, libraries, and other binaries, and configuration files needed to run it, bundled into one package. By containerizing the application platform and its dependencies, differences in OS distributions and the underlying infrastructure are abstracted away. A physical server running three VMs would have a hypervisor and three separate operating systems running on top of it. By contrast, a server running three containerized applications runs a single operating system, and each container shares the operating system kernel with the other containers. Dockers have become synonymous with container technology because it has been the most successful at popularizing it.