CoreOS is designed for security, consistency, and reliability. Instead of installing packages via yum or apt, CoreOS uses Linux containers to manage your services at a higher level of abstraction. A single service's code and all dependencies are packaged within a container that can be run on one or many CoreOS machines.
Linux containers provide similar benefits as complete virtual machines, but focused on applications instead of entire virtualized hosts. Since containers don’t run their own Linux kernel or require a hypervisor, they have almost no performance overhead. The lack of overhead allows you to gain density which means fewer machines to operate and a lower compute spend.