Kubelet a node agent that executes as a process directly in the nodes' operating system and not as a container. A kubelet ensures that the Pods that are scheduled to its node have their containers up and running and that they are healthy. It acts as a conduit between the api-server and the container runtime on its node.

kube-proxy, a network proxy that enables the Service concept in Kubernetes and is capable of forwarding requests to the appropriate Pods, typically in a round-robin fashion if more than one Pod is available for the specific Service. kube-proxy is deployed as a DaemonSet.

Container runtime, which is the software that runs the containers on a node. Historically, Kubernetes used Docker, but today any implementation of the Kubernetes Container Runtime Interface (CRI) can be used, for example, cri-o (https://cri-o.io) and containerd (https://containerd.io/).