Hello, hamza11.
SDN is short for a software-defined network.
Different from traditional networks where routing and forwarding nodes work independently, SDN introduces a central control node: the controller, to uniformly direct data from lower-layer devices to the destination. Lower-layer network devices only need to execute the data. In this way, just like the network has a brain, the control plane and forwarding plane can be separated, greatly enhancing network flexibility and scalability.

Hope this information is helpful to you.