What is a DNS operation?

The Domain Name System (DNS) is a general-purpose database for managing host information on the Internet.
It supports any kind of data, including network address, ownership, and service configuration, to be associated with hierarchically structured names.
It is primarily used to translate human-readable names of Internet resources to their corresponding IP addresses There is two important operation is dns forward lookup zone dns reverse lookup zone I hope was helpful, vote if it is

The Domain Name System (DNS) is a hierarchical distributed naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities. Most prominently, it translates easily memorized domain names to the numerical IP addresses needed for the purpose of locating computer services and devices worldwide. The Domain Name System is an essential component of the functionality of the Internet.

Domain  name server  is the smartest way to find a website .You cannot remember many website ip address at same time.So domain name is used for remembering the website.For example74.125.239.17 is one ip address of Google.com.It is very difficult to remember always.So you can use domain name to view the particular website. the conversion of domain name to ip address is done by DNS . If you want to find  domain to ip,ip to domain,dns record details  you can visit this site WhoisXY.com here you can get all the information

DNS server is responsible for converting name to IP vice-versa.Like in standard networking system, every host/computer is addressed by IP.So, when you type www.yahoo.com who converts to IP address? It is DNS Server.
Check the following link to understand about DNS operation or how it works: http://cr.yp.to/djbdns/intro-dns.html  

بروتوكول DNS يعمل على تحويل النص الى عنوان IP addressوالعكس

When you type (for instance www.example.com) in web browser, browser first check with operating system for  www.example.com if there is any entry for this address. Operating system is configured to ask DNS for IP addresses if it does not know. Resolving server is workforce of DNS loockup which is either configured manually or automatically within your operating system. Your operating system asks a query to resolving server for www.example.com. Resolving server may or may not have it in its cache memory, if it doesn't have in the memory then it will forward the query to "The root name servers" which would be  .com server in this case. The root name server give the information about com  name server, resolving name server takes all this information, put in its cache and then goes to com TLD server.

TLD sever says I don't know about this but I do know where to find the example.com name servers. The next stage of severs are Authoritative name servers.

With the help of the Registrar COM TLD NAME SERVERS knows which and where is Authoritative name server. When a domain is purchased a registrar is told with authoritative name server that which domain should use. They notify the organization for top level domain registry and tell them to update TLD name server.

The information comes back from same channel and now authoritative name will provide the www.example.com information and says tell your browser to go to the IP address192.168.1.1. The resolving name server takes this information, puts in the cache and gives that reply to operating system. Operating system then gives it to the browser and browser then makes a connection with192.168.1.1 www.example.com. The whole process takes less than a second to complete because DNS are designed to work very fast.

give a brief descriptio of dns operation