While Docker had been for the longest time the name you are most probably to hear when ever the discussion of containers run time come up, lately containerd has becoming so popular that you are hearing it just as often. The fun part which confuse many people is that containerd is used by Docker. The code that makes up containerd was originally part of the Docker Daemon but was abstracted from it to provide a more modular approach.

containerd is an OCI compliant core container runtime designed to be embedded into larger systems such as Kubernetes. It provides the minimum set of functionality to execute containers and manages images on a node. It was initiated by Docker Inc. and donated later to CNCF. The Docker engine itself is built on top of containerd.