Pod replicas can be created using ReplicaSets
One Pod template, multiple replicas

networkandcode@cloudshell:~ (kubernetes-cka-224606)$ kubectl get rs
No resources found.
networkandcode@cloudshell:~ (kubernetes-cka-224606)$ kubectl get pods
No resources found.
networkandcode@cloudshell:~ (kubernetes-cka-224606)$ cat ex6.yml

---
#ReplicaSet is an object that contains replicas of a Pod
apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: rs6
  namespace: default
spec:
  replicas: 3  #there will be 3 replicas of the same Pod
  selector:
    matchLabels:
      tag: label6  #the replicaSet should pick Pods with this label
  template:  #the Pod template
    metadata:  #Pod name need not be defined as replicaset takes care of it
      labels:
        tag: label6
    spec:
      containers:
      - name: ctr6
        image: nginx
...

networkandcode@cloudshell:~ (kubernetes-cka-224606)$ kubectl create -f ex6.yml
replicaset.apps/rs6 created

networkandcode@cloudshell:~ (kubernetes-cka-224606)$ kubectl get rs
NAME DESIRED CURRENT READY AGE
rs6 3 3 3 1m

networkandcode@cloudshell:~ (kubernetes-cka-224606)$ kubectl get pods
NAME READY STATUS RESTARTS AGE
rs6-274lv 1/1 Running 0 11s
rs6-rp6jj 1/1 Running 0 11s
rs6-vnc4r 1/1 Running 0 11s

networkandcode@cloudshell:~ (kubernetes-cka-224606)$ kubectl delete pods rs6-274lv
pod "rs6-274lv" deleted

Even when a Pod is deleted, the replicaSet would ensure its replaced by another Pod so that the number of replicas remain the same
networkandcode@cloudshell:~ (kubernetes-cka-224606)$ kubectl get pods
NAME READY STATUS RESTARTS AGE
rs6-pzxwd 1/1 Running 0 11s
rs6-rp6jj 1/1 Running 0 1m
rs6-vnc4r 1/1 Running 0 1m

Once the replicaSet is deleted, the Pods are also deleted
networkandcode@cloudshell:~ (kubernetes-cka-224606)$ kubectl delete rs rs6
replicaset.extensions "rs6" deleted
networkandcode@cloudshell:~ (kubernetes-cka-224606)$ kubectl get pods
NAME READY STATUS RESTARTS AGE
rs6-4krtz 0/1 Terminating 0 1m
rs6-829r6 0/1 Terminating 0 1m
rs6-x58v5 0/1 Terminating 0 1m
networkandcode@cloudshell:~ (kubernetes-cka-224606)$ kubectl get pods
No resources found.

Reference:
https://kubernetes.io/docs/concepts/workloads/controllers/replicaset/

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