Rudimentary info for newbies: LXC is a userspace interface for the Linux kernel containment features. Through a powerful API and simple tools, it lets Linux users easily create and manage system or application containers. It has more capability than a chroot environment but less than a full virtual machine environment.
We have a container basics article [1] that provides a quick overview of Linux containers including differences between LXC and Docker containers.
Linux containers are made possible by the addition of Linux namespaces to the kernel in 2.6. A namespace allows you to launch an isolated process. There are 6 main namespaces including a network namespace and container managers basically launch the container process in a new namespace.
LXC is a userland container manager in development since 2008. Docker was initially based on LXC in 2013 and later developed their own container manager in Go.
LXC launches an OS init in the namespace so you get a standard multi process OS environment like a VM. Docker launches the application process directly so you get a single process container. Docker also uses layers to build containers and has ephemeral storage.
So LXC containers behave more or less like lightweight VMs. Docker is doing a few more things that need to be understood.
The salient point: both LXC and Docker, and any other "container" solution, use the same Linux kernel features that implement containment: chroot and FS mounting to make the container's view of filesystem, namespaces to make the container's view of uids / gids, processes, and other resources around it, and virtual network interfaces + packet filtering to produce the container's view of the networking environment.
On top of this, Docker and LXC offer different ways to build, run, and orchestrate containers. So do other container engines, such as rkt.
