What is the significance of User Plane and Control Plane?

What is the significance of user plane and control plane? Its usage?
And how the separation between both of them is possible in 5G?

At User Plane side, the application creates data packets that are processed by protocols such as TCP, UDP and IP.
While in the Control Plane, the radio resource control (RRC) protocol handles the signalling messages that are exchanged between the base station and the mobile.
The main motivation for CUPS is to make user plane functions scale independently, allowing operators for a more flexible deployment and dimensioning of the network.
For example, if data traffic increases, more data plane (UP) nodes can be added without affecting the control plane functions.

Please correct me if I am wrong: CUPS is the main driving factor for latency reduction in NR.

Yes, You’re right. We have some major requirements in 5G
Such as ultra-low latency and ultra-high throughput - require highly flexible RAN architecture and topology.
This will be enabled only by splitting RAN functions like CUPS.

OK.
Got it now, thanks.

Not every entity in the Architecture is communicating each other.
Hence separation is possible.

Add CU-DU split as well.

Centralized Unit – Distributed Unit (CU-DU) Split Base Station | 5G Systems Base Station Architecture

​There are different base station architecture types specified in 5G Systems (5GS):

  • Standalone Base Station
  • Non-Standalone Base Station
  • CU-DU Split Base Station

In this link you can read about Centralized Unit (CU) - Distributed Unit (DU) Split Base station architecture.

Maybe this post can help you to understand similarities between 4G and 5G core: