Docker is best known for its capability to build and run containers. This is how we have used the term "Docker" in the Tech Radar recently. But Docker is also a complete production platform, where the capability to build and run Containers is only a small fraction of its capabilities. At the same time numerous alternate runtimes for containers – like containerd and podman – as well as image builders – like Kaniko and Buildah – have evolved during the last years. Thanks to the standards established by the Open Container Initiative these tools are mostly interchangeable for the purposes of building and running containers.
To be more distinct, we now recommend using Containers and Runtimes as specified by the Open Container Initiative. Docker is one of many tools to achieve that.