Kubernetes uses Readiness Probes to know when a container is ready to start accepting traffic. A Pod is considered ready when all of its containers are ready. One use of this signal is to control which Pods are used as backends for Kubernetes Services (and esp. Ingress).

Kubernetes uses Liveness Probes to know when to restart a container. For example, Liveness Probes could catch a deadlock, where an application is running, but unable to make progress. Restarting a container in such a state can help to make the application more available despite bugs, but restarting can also lead to cascading failures (see below).