In addition to API groups, another useful classification of the available APIs is functionality. The Kubernetes API is huge, and breaking it down into categories helps a lot when you're trying to find your way around. Kubernetes defines the following resource categories:

• Workloads: The objects you use to manage and run containers on the cluster.
• Discovery and load balancing: The objects you use to expose your workloads to the world as externally accessible, load-balanced services.
• Config and storage: The objects you use to initialize and configure your applications, and to persist data that is outside the container.
• Cluster: The objects that define how the cluster itself is configured; these are typically used only by cluster operators.
• Metadata: The objects you use to configure the behavior of other resources within the cluster, such as HorizontalPodAutoscaler for scaling workloads.

In the following subsections, I'll list the resources that belong to each group, along with the API group they belong to. I will not specify the version here because APIs move rapidly from alpha to beta to general availability (GA), and then from V1 to V2, and so on.