It scheduling a pod on a specific node.
It specifies a map of 'KEY=VALUE' pairs.
The Node should have each of 'KEY=VALUE' pairs labels as used for the Pod.
For a Node need to configure 'KEY=VALUE' pairs Labels. 
The Node 'KEY=VALUE' pairs labels are mapped/configured with Pod.

The some default built-in node labels such as
-> beta.kubernetes.io/arch=amd64
-> beta.kubernetes.io/os=linux
-> kubernetes.io/arch=amd64
-> kubernetes.io/hostname=HOSTNAME
-> kubernetes.io/os=linux
-> node-role.kubernetes.io/control-plane=
The values of these labels may vary depending on the environment (eg: OS), Cloud Provider, etc.
