What is an 'endpoint' in Kubernetes?

While you're correct that in the glossary there's indeed no entry for endpoint, it is a well defined Kubernetes network concept or abstraction. Since it's of secondary nature, you'd usually not directly manipulate it. There's a core resource Endpoint defined and it's also supported on the command line:

$ kubectl get endpoints
NAME         ENDPOINTS            AGE
kubernetes   192.168.64.13:8443   10d

And there you see what it effectively is: an IP address and a port. Usually, you'd let a service manage endpoints (one EP per pod the service routes traffic to) but you can also manually manage them if you have a use case that requires it.

Pods expose themselves through endpoints to a service. It is if you will part of a pod.

Source: Services and Endpoints

An endpoint is an resource that gets IP addresses of one or more pods dynamically assigned to it, along with a port. An endpoint can be viewed using kubectl get endpoints.

An endpoint resource is referenced by a kubernetes service, so that the service has a record of the internal IPs of pods in order to be able to communicate with them.

We need endpoints as an abstraction layer because the 'service' in kubernetes acts as part of the orchestration to ensure distribution of traffic to pods (including only sending traffic to healthy pods). For example if a pod dies, a replacement pod will be generated, with a new IP address. Conceptually, the dead pod IP will be removed from the endpoint object, and the IP of the newly created pod will be added, so that the service is updated and 'knows' which pods to connect to.

Read 'Exposing pods to the cluster', then 'Creating a Service' here - https://kubernetes.io/docs/concepts/services-networking/connect-applications-service/#exposing-pods-to-the-cluster

An easy way to investigate and see the relationship is:

• kubectl describe pods - and observe the IP addresses of your pods
• kubectl get ep - and observe the IP addresses assigned to your endpoint
• kubectl describe service myServiceName - and observe the Endpoints associated with your service

So no, the endpoint isn't anything to do with the IP of an individual node. I find it useful to understand the overall structure of kubernetes and the relationship between the cluster, nodes, services, endpoints and pods. This diagram summarises it nicely, and shows an ingress flow that results in the OSI layer 2 (the TCP layer) reaching a back end Node 1, with the OSI layer 7 (http layer) ingress ultimately reaching 'Web Container 1' in Pod 1: