Webhooks allow Operator authors to intercept, modify, and accept or reject resources before they are saved to the object store and handled by the Operator controller. Operator Lifecycle Manager (OLM) can manage the lifecycle of these webhooks when they are shipped alongside your Operator.
See Generating a ClusterServiceVersion (CSV) for details on how an Operator developer can define webhooks for their Operator, as well as considerations when running on OLM.