NS-3 is an open-source network simulator designed for research and educational purposes. It allows users to create and simulate complex network scenarios, enabling the study of various protocols and network behaviors without the need for physical hardware. The simulator supports a wide range of network technologies, including Wi-Fi, LTE, and TCP/IP. Researchers and developers can use NS-3 to test new ideas, analyze performance, and visualize network interactions, making it a valuable tool in the field of computer networking.