Webhooks are requests for information sent in a blocking fashion. A web application implementing webhooks will send an HTTP request to other application when certain event happens.
In controller-runtime libraries, we support admission webhooks and CRD conversion webhooks.
Kubernetes supports these dynamic admission webhooks as of version 1.9 (when the feature entered beta).
Kubernetes supports the conversion webhooks as of version 1.15 (when the feature entered beta).