First, a little background. Clouds are built on virtual machine (VM) hypervisors such as Hyper-V, KVM, and Xen. While you can run multiple VMs on a server, since each VM contains an entire operating system, they’re fat in terms of system resources.
Containers, on the other hand, use shared operating systems, That makes them skinnier. In turn, that means containers let you run more apps on a server than a VM will, and that gives you more value from your server hardware investment.