What is the difference between Master Node and Control Plane on Kubernetes?

Have a look at https://github.com/kubernetes/kubernetes/blob/master/CHANGELOG/CHANGELOG-1.20.md#urgent-upgrade-notes . This should answer your Question:

• The label applied to control-plane nodes "node-role.kubernetes.io/master" is now deprecated and will be removed in a future release after a GA deprecation period.
• Introduce a new label "node-role.kubernetes.io/control-plane" that will be applied in parallel to "node-role.kubernetes.io/master" until the removal of the "node-role.kubernetes.io/master" label.

I think also important is this:

• Make "kubeadm upgrade apply" add the "node-role.kubernetes.io/control-plane" label on existing nodes that only have the "node-role.kubernetes.io/master" label during upgrade.
• Please adapt your tooling built on top of kubeadm to use the "node-role.kubernetes.io/control-plane" label.
• The taint applied to control-plane nodes "node-role.kubernetes.io/master:NoSchedule" is now deprecated and will be removed in a future release after a GA deprecation period.
• Apply toleration for a new, future taint "node-role.kubernetes.io/control-plane:NoSchedule" to the kubeadm CoreDNS / kube-dns managed manifests. Note that this taint is not yet applied to kubeadm control-plane nodes.
• Please adapt your workloads to tolerate the same future taint preemptively.

Same thing, we switched to the "control plane" terminology about a year ago as it is more accurate and doesn't have problematic cultural undertones.

Control Plane hosts important components like api-server,etcd,kube-scheduler and kube-controller in your kubernetes cluster. As said, it is same as Master Node just a terminology change pretty lately.