Logical separation / division of resources based on Org / Project.
A pod is the smallest execution unit in Kubernetes. A pod encapsulates one or more applications. Pods are ephemeral by nature, if a pod (or the node it executes on) fails, Kubernetes can automatically create a new replica of that pod to continue operations.
A ReplicaSet (RS) is a Kubernetes object used to maintain a stable set of replicated pods running within a cluster at any given time. A Kubernetes pod is a cluster deployment unit that typically contains one or more containers.
A Deployment manages a set of Pods to run an application workload, usually one that doesn't maintain state.