Kubernetes creates DNS records for Services and Pods. You can contact Services with consistent DNS names

instead of IP addresses.

1.

2. Every Service defined in the cluster is assigned a DNS name.

3. By default, a client Pod's DNS search list includes the Pod's own namespace and the cluster's default domain

If are pod on test namespace and service in prod namespace then without specifying the namespace it not

possible that we can find service from the test namespace.

4.

5. For more details about dns refer this link