nslookup is a command-line tool used in cybersecurity and network administration to query Domain Name System (DNS) records. It helps users obtain information about domain names, IP addresses, and DNS servers. By entering a domain or IP address, nslookup retrieves DNS records such as A, MX, and CNAME, which are essential for diagnosing network issues. This tool is widely used for troubleshooting connectivity problems, verifying DNS configurations, and detecting potential DNS spoofing attacks. nslookup is available on most operating systems, making it a versatile and essential utility for IT professionals and cybersecurity experts.