Virtualization over the past years has become a key strategy for IT to acquire multi-tenancy, increase utilization, develop elasticity and improve security. And virtual machines (VMs) are quickly becoming a main vehicle for developing and deploying applications. The introduction of containers seems to be bringing another and perhaps overlapped solution for achieving the same above-mentioned benefits. Are a container and a virtual machine fundamentally the same or different? And how? Is one technically superior to the other? What about performance and security? Does IT need either one, or both?