DNS lookup (also known as a DNS query) is the process of finding the IP address associated with a domain name. When you enter a domain name in your web browser, your computer sends a DNS lookup request to a DNS server to resolve the domain name into an IP address, which is used to establish a connection with the website's server.
DNS is like a phone book for the Internet, mapping domain names to IP addresses so that computers can communicate with each other. A DNS lookup typically involves multiple steps, including querying local DNS cache, sending the request to a recursive DNS server, and finally, receiving a response from an authoritative DNS server with the desired IP address.
DNS lookup is an essential part of how the Internet works, and without it, you would have to remember the IP addresses of all the websites you want to visit instead of using human-friendly domain names.