DNS: DNS stands for Domain Name System or Domain Name Server. Essentially, it serves as a naming scheme mechanism for different domain names on the internet and pairs them with a numerical IP (internet protocol) address.
Domain names and IP addresses comprise the two different types of namespaces on the internet. These two addresses together help to organize websites on the internet, and they are especially useful if a domain name changes, as it will still route to the same IPv4 and IPv6 addresses.
The process for domain name syntax, or naming a domain, has a lot to do with the hierarchy of the domain name system. A .com address is considered a top-level domain and resides to the right of the domain name. A subdomain is the www. prefix and is on the left side of the domain name. A full domain name must not be longer than 253 characters. Finally, they must all have a hostname, which has an IP address associated with it. Example.com and www.example.com would be hostnames, whereas simply .com would not be.
Registrars, who register domain names for webmasters, must comply with the Internet Corporation for Assigned Names and Numbers (ICANN). The Internet Engineering Task Force is responsible for developing requirements for domain names and other aspects of DNS protocol. Different domain names and DNS software are vulnerable to hackers. The practice of phishing (or using malicious means to gather internet users' personal information) is sometimes the result of similarly named domains; in other words, a hacker may use face-book.com instead of facebook.com to get users' log-in credentials.