What are containers and why do you need them?

What other benefits do containers offer? A container may be only tens of megabytes in size, whereas a virtual machine with its own entire operating system may be several gigabytes in size. Because of this, a single server can host far more containers than virtual machines. Applications built in this way are easier to manage because each module is relatively simple, and changes can be made to modules without having to rebuild the entire application. Because containers are so lightweight, individual modules (or microservices) can be instantiated only when they are needed and are available almost immediately. [...]container technology is not new; it has been built into Linux in the form of LXC for over 10 years, and similar operating system level virtualization has also been offered by FreeBSD jails, AIX Workload Partitions and Solaris Containers. The project's sponsors include AWS, Google, IBM, HP, Microsoft, VMware, Red Hat, Oracle, Twitter, and HP as well as Docker and CoreOS Why are all these companies involved in the Open Container Initiative? (Microsoft also introduced Hyper-V containers, which are Windows containers running in a Hyper-V virtual machine for added isolation.) Windows containers can be deployed on a standard install of Windows Server 2016, the streamlined Server Core install, or the Nano Server install option which is specifically designed for running applications inside containers or virtual machines. [...]the management tools that are available to orchestrate large numbers of containers are also not yet as comprehensive as software for managing virtualized infrastructure, such as VMware's...