The Top-Level Domain Names

The official list of all top-level domains is maintained by the Internet Assigned Numbers Authority (IANA). Basically there are two types of top-level domains: generic (also known as global) and country code. Generic Top Level Domains (gTLD) were created to be used by the Internet public, while country code Top Level Domains (ccTLD) were created to be used by each individual country, as they deem necessary.

Generic Top Level Domains (gTLD)
The most popular generic Top Level Domains are as follows: .com .net .org .biz .info .edu .mil .gov.

.com represents the word "commercial," and is the most widely used extension in the world. Most businesses prefer a .com domain name because it is a highly recognized symbol for having a business presence on the Internet.

.net represents the word "network," and is most commonly used by Internet service providers, Web-hosting companies or other businesses that are directly involved in the infrastructure of the Internet. Additionally, some businesses choose domain names with a .net extension for their intranet Websites.

.org represents the word "organization," and is primarily used by non-profits groups or trade associations.

.biz is used for small business Web sites.

.info is for credible resource Web sites and signifies a "resource" web site. It's the most popular extension beyond .com, .net and .org.

.mobi (short for "mobile") is reserved for Web sites built for easy viewing on mobile devices.

.tv is for rich content/multi-media Web sites, commonly used within the entertainment or media industry.

.name is the only domain extension specifically designed for personal use. It is commonly used for easy to remember e-mail addresses and personal web sites that display photos or personal information about an individual.

country code Top Level Domains (ccTLD)
The most popular country code Top Level Domains (ccTLD) are as follows: .cn (China), .de (Germany), .uk (United Kingdom), .nl (Netherlands), .eu (European Union), .ar (Argentina), etc.

You can learn more List of Internet top-level domains here.