a liveness probe tells Kubernetes if a Pod needs to be replaced and a readiness probe tells Kubernetes if its Pod is ready to accept requests. To simplify this work, Spring Boot has added support for implementing liveness and readiness probes. The probes are exposed on the URLs /actuator/health/liveness and /actuator/health/readiness. They can either be declared by configuration or implementation in source code, if increased control is required compared to what configuration gives. When declaring the probes by configuration, a health group can be declared for each probe specifying what existing health indicators it should include. For example, a readiness probe should report DOWN if a microservice can't access its MongoDB database. In this case, the health group for the readiness probe should include the mongo health indicator

Liveness Probe — monitors the availability of an application while it is running. If a liveness probe fails, Kubernetes will restart your pod. This could be useful to catch deadlocks, infinite loops, or just a “stuck” application.

readiness probe - monitors when your application becomes available. If a readiness probe fails, Kubernetes will not send any traffic to the unready pods and the endpoint controller removes the pod from all services. This is useful if your application has to go through some configuration before it becomes available, or if your application has become overloaded but is recovering from the additional load. By having a readiness probe fail, your application will temporarily not get any more traffic…  

A liveness probe is a diagnostic check that determines if a container is running properly. If a container fails the liveness probe, Kubernetes will restart the container, attempting to resolve the issue.