Containers help to create a separate environment in which software can run. The software has exclusive use of the entire user area. Any modifications made inside a container have no effect on the server or other containers on the same host.
Moreover, containers are an application layer abstraction, and each container represents a distinct application. In the case of virtualization, hypervisors provide the guest with an entire virtual machine, like Kernel. VMs are a hardware layer abstraction, and each virtual machine is a physical machine.
