To understand Kubernetes, it is important to realize that running containers directly is a bad option for most use cases. Containers are low-level entities that require a framework on top. They need something that will provide all the additional features we expect from services deployed to clusters. In other words, containers are handy but are not supposed to be run directly.

The reason is simple. Containers, by themselves, do not provide fault tolerance. They cannot be deployed easily to the optimum spot in a cluster, and, to cut a long story short, are not operator friendly. That does not mean that containers by themselves are not useful. They are, but they require much more if we are to harness their real power. If we need to operate containers at scale, be fault tolerant and self-healing, and have the other features we expect from modern clusters, we need more. We need at least a scheduler, probably more.