For someone who still doesn't quite get Docker, this sort of brief enumeration is incredibly useful. Is there something similar for Kubernetes?
Second, Kubernetes is a dev-friendly app management tool. Start 5 copies of this app, restart if it fails, mount this config file, etc. Most Kube apps look roughly the same across teams and companies, so skills are transferrable.
Third, the Kubernetes API is a standardization layer between compute/cloud capabilities.
Fourth, the Kubernetes Container <foo> Interface (CxI) is a implementation layer to plug in to compute capabilities. You can swap Docker, CRI-O, etc with the Container Runtime Interface (CRI). Use cloud block storage with Container Storage Interface (CSI).
Fifth, Kubernetes custom resources (CRDs) are a standardized extension point for building custom behavior into a cluster in a sane way.
1) an API server and spec definition for infrastructure and applications
2) a distributed database to store API state
3) agents to apply the API definition into “real” systems