Nmap, short for Network Mapper, is a free and open-source tool used for network discovery and security auditing. It is a highly effective and adaptable network scanning tool that can be used for vulnerability checking, port scanning, and network mapping. Nmap uses raw IP packets in novel ways to determine what hosts are available on the network, what services those hosts are offering, what operating systems they are running, what type of packet filters/firewalls are in use, and dozens of other characteristics. It was designed to rapidly scan large networks, but works fine against single hosts.

Nmap is widely used by network and system administrators for tasks such as network inventory, managing service upgrade schedules, and monitoring host or service uptime. It is also used for penetration testing and ethical hacking, as it can help identify potential vulnerabilities in a network. Nmap is platform-agnostic and can be run on various standard operating systems, including Linux, Windows, macOS, and BSD. It includes both a command-line interface (CLI) and a graphical user interface (GUI), making it straightforward to use.

Some of the most useful scans that can be run with Nmap include TCP Scan/TCP Connect Scan, UDP Scan, and Ping Scan/NO PORT Scan. Nmap can also be used for network mapping, which shows the user what types of devices are connected to the network and how they are connected.

In summary, Nmap is a powerful and flexible tool that can be used for a variety of tasks related to network discovery and security auditing. It is widely used by network and system administrators, as well as by ethical hackers and security professionals.