PVs are resources in the cluster. PVCs are requests for those resources and also act as claim checks to the resource.
To be more clear, A PersistentVolume (PV) is a piece of storage in the cluster, It is a resource in the cluster just like a node is a cluster resource. PVs are volume plugins like Volumes but have a lifecycle independent of any individual pod that uses the PV.
A PersistentVolumeClaim (PVC) is a request for storage by a user. It is just like a Pod, pods requests for resources like CPU and memory, while PVC requests for specific size of PV and access modes.