Docker is a platform and family of tools that allow Linux applications to be packaged along with all of their dependencies (libraries, etc.) to create a ready-to-run image. The Docker ecosystem includes an application registry called the Docker Hub Registry to allow searching and downloading of application images; a Linux container-based runtime environment to execute them ("Docker Engine"); and a growing collection of cluster management tools to orchestrate, scale and manage applications ("Docker Machine, Swarm and Compose").
Today many Docker applications run in containers within VMs hosted on hypervisors such as XenServer and other distributions of Xen. The synergy between containers as an application isolation mechanism and hypervisors as a secure physical infrastructure virtualization mechanism is something we believe strongly in. That's why we've been looking at how we can enhance XenServer to be a great platform for Docker applications and how we can contribute to the Docker ecosystem to best leverage the capabilities and services available from the hypervisor.
Docker support for XenServer is a feature of XenServer 6.5 SP1 and can be downloaded from the XenServer download page. The support is delivered as a supplimental pack named "xs-container" which also includes support for CoreOS and cloud-drives.