Correct, Docker is currently based on lxc, but that is an implementation detail. In theory it could be ported to any process-level isolation tech with similar f

Correct, Docker is currently based on lxc, but that is an implementation detail. In theory it could be ported to any process-level isolation tech with similar features: OpenVZ, Solaris Zones - you could also try using BSD jails although I don't know if they have all the required features. To answer the original question: Docker extends LXC with a higher-level API which operates at the process level. OpenVZ helps you create "mini-servers". Docker lets you forget about servers and manage processes.