ipBlock defines policy on a particular IPBlock. If this field is set then neither of the other fields can be.

namespaceSelector selects namespaces using cluster-scoped labels. This field follows standard label selector semantics; if present but empty, it selects all namespaces. If podSelector is also set, then the NetworkPolicyPeer as a whole selects the pods matching podSelector in the namespaces selected by namespaceSelector. Otherwise it selects all pods in the namespaces selected by namespaceSelector.

podSelector is a label selector which selects pods. This field follows standard label selector semantics; if present but empty, it selects all pods. If namespaceSelector is also set, then the NetworkPolicyPeer as a whole selects the pods matching podSelector in the Namespaces selected by NamespaceSelector. Otherwise it selects the pods matching podSelector in the policy's own namespace.