A root server usually refers to a root name server which ensures that Internet addresses in word-form can be translated into IP addresses via the DNS. Without root servers, Internet addresses as we use them today would not be possible. Hosts are often incorrectly called root servers as well. However, these servers have nothing in common with a root name server.
The root server purpose is to ensure that the assignment of IP addresses to web addresses runs successfully. In principle, the root server handles the administration of only a single file. This file includes all information that is necessary so that the Domain Name System (DNS) works. The root server permanently evaluates the stored file using a fixed hierarchy and assigns top level domains to IP addresses. It answers queries about a top-level domain if the name server is not responding. This task is performed permanently by the various root servers around the world, when a client (such as a web browser) wants to access a website.
You could therefore call a root server a central interface for communication between users and web content. Without the work of root servers, there would be chaos on the Internet. They are somewhat like the top administrative level for address assignment, a kind of “land registry of the Internet.” Without the root name servers there would be no functioning web addresses.
The work of root servers is coordinated by ICANN (Internet Corporation for Assigned Names and Numbers). This organization checks whether registrations of domains and changes of domain names are technically correct. Subsequently these changes are reflected in the system of root servers.
Example of the operation of a root server:
A user types the address www.ryte.com into the address bar of their browser. In order for the client to be able to connect with the appropriate IP address and retrieve the corresponding data from the server, this address must be converted into IP format. If it is not in the cache of the computer, it will send a DNS query to the appropriate DNS server of the provider. If the IP is not stored there either, the appropriate root server is queried. The root server issues the registrar, based on which the URL can be resolved into an IP address that is passed to the requesting computer, so that it can be read by the browser. The root server is thus the last possible entity that can resolve a web address into an IP address.
There are 13 genuine root servers and over 100 different instances worldwide are responsible for the coordination of domain names. In addition to the root servers managed by ICANN, there are also alternative projects.
The term root server is often colloquially used to refers to a host. What is meant is a server that is not shared with other clients (such as is the case with a shared server). If you hire a “root server,” i.e. a host, you will get your own IP address and additional administrative rights.
Hosts are especially of interest to search engine optimization because through them is can be ensured that a website will be regarded as more trustworthy by Google and other search engines than a site that shares its server space with other websites. With your own host there is also no risk of getting in the vicinity of a “bad neighborhood” at the server level.