Need clarification for "postgresql-client: 'true'" label in template

template:
metadata:
labels:
annotations:
prometheus.io/path: {{.Values.contextPath}}/management/prometheus
prometheus.io/port: “8099”
prometheus.io/scrape: “true”
labels:
app: {{ .Release.Name }}
app.kubernetes.io/name: {{ .Release.Name }}
app.kubernetes.io/version: {{ .Values.imageTag }}
ingress-communication: “true”
postgresql-client: “true”

Above is the cropped content of my deployment.yaml file, I have spring boot application which does connect to Postgresql DB. I am not able to understand only if I mention “postgresql-client: “true”” then only my connection establish with DB server ( which is defined in another namespace, I use service to connect to DB), else connection is getting timeout.

Can you please let me know the importance of postgresql-client: “true” label in POD specification. And where do I get the more information about such tricky configurations

++ any help appreciated
Regards,
Kiran.