Acronym. Domain Name Server.
When using a Web Browser, DNS takes the part between "http://" and the first slash "/" and converts it into an IP Address, which is a very large number which uniquely identifies a web server on the internet.
For example for the web address:
DNS takes the term www.example.com and converts it into an IP address: 184.108.40.206
DNS is used as the primary way of converting names on the internet to addresses. Any application which accesses the internet uses DNS first to find a server. Because DNS is the first step used in any internet transaction, it is the target of security breaks.
DNS is used by the following applications:
On Linux, FreeBSD, Mac OS X, or any variant, you can use a command line tool (using iTerm, Terminal, xterm, or some similar shell tool) to perform DNS on the fly using the host command:
> host www.example.com www.example.com has address 220.127.116.11
On Windows, to perform DNS requests, go to the Start Menu, then Run ..., and type in nslookup:
Default Server: acumen Address: 192.168.0.1
> www.example.com Server: acumen Address: 192.168.0.1
Non-authoritative answer: Name: www.example.com Address: 18.104.22.168
You can just enter the name you wish to resolve and it will output the response from your local DNS server.