Containers are used by Warewulf as the template for the VNFS image. Warewulf containers can be any type of OCI or Singularity standard image formats but maintained on disk as an "OCI bundle". Warewulf integrates with Docker, Docker Hub, any OCI registery, Singularity, standard chroots, etc.
The controller node(s) are the resources responsible for management, control, and administration of the cluster. Historically these systems have been called "master", "head", or "administrative" nodes, but we feel the term "controller" is more appropriate and descriptive of the role of this system.
Worker nodes are the systems that are being provisioned by Warewulf. The roles of these systems could be "compute", "storage", "GPU", "IO", etc. which would typically be used as a prefix, for example: "compute worker node"