A Network Simulator is a software tool that allows users to create and analyze network configurations without the need for physical hardware. It simulates the behavior of network devices, such as routers and switches, enabling users to test various scenarios, protocols, and performance metrics. This is particularly useful for educational purposes, research, and network design. By using a network simulator, users can visualize how data flows through a network and identify potential issues before implementation. Popular examples of network simulators include Cisco Packet Tracer and GNS3, which provide interactive environments for learning and experimentation in networking concepts.