There are multiple subcomponents running in the master and worker nodes, but unless we are operating the cluster ourselves, we can ignore these components for most of the time and treat it as a black box.

If you are curious, this is a more detailed (though still not 100% complete) view of the components running in the master and worker nodes.

Architecture of master and worker nodes

But as we said, most of the time we just need to know that we run kubectl locally, and that will send information to the master node, which will make things happen in the worker nodes.