Linux Containers (LXC) is an OS-level virtualization method for running multiple isolated Linux systems (containers) on a control host using a single Linux kernel.
LXC combines the Linux kernel’s cgroups – feature that limits, accounts for, and isolates the resource usage (CPU, memory, disk I/O, etc) of a collection of processes – and support for isolated namespaces to provide an isolated environment for applications.
Early versions of Docker (pre 1.10) used LXC as the container execution driver.
Source: Wikipedia
Related to Docker, see Difference with standard LXC s