Explanation
Application and systems logs can help you understand what ishappening inside your cluster. The logs are particularly useful for debugging problems and monitoring cluster activity. Most modern applications have some kind of logging mechanism; as such, most container engines are likewise designed to support some kind of logging. The easiest and most embraced logging method for containerized applications is to write to the standard output and standard error streams.
Kubernetes also provides cluster-based logging to record container activity into a central logging subsystem. The standard output and standard error output of each container in a Kubernetes cluster can be ingested using an agent like Fluentd running on each node into tools like Elasticsearch and viewed with Kibana. And finally, monitor containers, pods, applications, services, and other components of your cluster.
One can use tools such as Prometheus, Grafana, Jaeger for monitoring, visibility, and tracing the cluster.

References:
https://dzone.com/articles/5-best-security-practices-for-kubernetes-and-oracle-kubernetes-engine
https://kubernetes.io/docs/concepts/cluster-administration/logging/
https://blogs.oracle.com/developers/5-best-practices-for-kubernetes-security