ReplicaSet is next generation for ReplicationController.

[ReplicaSet]
It is Set-Based Selectors.
In code there will be difference in the syntax. ReplicaSet which contains 'matchLabels' field under the 'selector'.
#----------CODE----------#
apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: REPLICASET_NAME
spec:
  replicas: NO
  selector:
    matchLabels:                                                # This option was added
      KEY: VALUE
........
........
........
#------------------------#

[ReplicationController]
It is Equality-Based Selectors.
In code there will be difference in the syntax. ReplicationController which doesn't contains 'matchLabels' field under the 'selector'.
#----------CODE----------#
apiVersion: v1
kind: ReplicationController
metadata:
  name: REPLICATIONCONTROLLER_NAME
spec:
  replicas: NO
  selector:
    KEY: VALUE
........
........
........
#------------------------#
