When you type yahoo.com into your web browser, your browser sends a query over the Internet to find the website for yahoo.com. The first server you query interacts with is the recursive resolver, which is typically operated by your ISP. The recursive resolver knows which other DNS severs it needs to ask to get the IP for yahoo.com.
The 1st type of DNS server the recursive resolver talks to is called a root server. The root servers are running all over the world and each one knows the DNS information about TLD such as ‘.com’. The recursive resolver ask a root server for DNS information about ‘.com’. Each TLD’s DNS stores the address information for the second level domain (yahoo.com) within the top level domain (.com). When your query reaches the TLD server, the TLD server answers with the IP address of the domain’s nameserver which will provide the next piece of information. Next the recursive resolver sends the query to the domain’s nameserver. This DNS server knows the IP address for the full domain, yahoo.com, and that answer is returned to the recursive resolver.
Now, that the recursive resolver knows the IP address for the domain name in your query, the recursive resolver tells the browser what the IP address is. Finally, your browser can send a request to the website to retrieve the website’s content, using the IP address.