The Domain Name System (DNS) translates human-readable domain names into IP addresses.
When you type google.com, your browser doesn't know where to send packets. It asks a DNS server "what's the IP for google.com?" The server responds with something like . Now your browser can connect.
DNS uses UDP port for most queries. Large responses or zone transfers use TCP port . Without DNS, you'd need to memorize IP addresses for every website you visit.