Domain Name System
The TCP/IP protocol that is used to send data between nodes on a network requires that all devices on a network must have a unique identifier known as the IP address. IP addresses are represented by four numbers, each ranging from 0 to 255, separated by a dot. An IP address can therefore be anything between 0.0.0.0 and 255.255.255.255.
Since such IP addresses are not user-friendly or easy to remember, the Domain Name System (DNS) was created to assign user-friendly names to each IP address. A domain name consists of two or more parts that are separated by a dot. For example, one of the most widely used domain names would be google.com.
Domain names are structured as a hierarchy. Going from right to left, each part on the left of a dot specifies a child of the part on its right. The right-most part specifies what is known as a top-level domain (TLD). Top-level domains indicate a category of establishments. For example, .com is used for global commercial businesses, .edu is used for educational institutes, .gov is used for government organizations, and so on. Top-level domains (TLDs) started with a small set but today have expanded to include countries (for example, .co.in is used for commercial businesses in India and so on), and specific business types (.bank, .tv, and so on).
Some TLDs are restricted to entities that meet certain criteria, such as .edu can only be assigned to a registered educational institute, while others like .com are open for anyone to use, including individuals.
The next part is the name of the entity. For example, google.com or stanford.edu, are domain names specifically assigned to Google as a business and Stanford as an educational institute. These two parts of the domain name must be globally unique combinations. No two entities can be assigned the same two-part domain name. For example, you cannot have two businesses with google.com or two educational institutes with stanford.edu, but you can have google.com and google.co.in (a domain for Google globally and another one for Google in India).
The first part, such as www, as in www.google.com or www.standford.edu is the reference to the actual node on the network. This three-part domain name is now mapped to a unique IP address. Now, instead of needing to remember an IP address for a device, you can remember a far more user-friendly domain name.
One of the global entities that manage the Internet, ICANN, along with a global network of Domain Registrars, usually one in each country, managing the allocation of unique domain names. Ideally, a business, an academic institute, or any other entity would prefer a domain name that matches its name exactly. When allocating domain names, as far as possible, exact matches to registered names are allocated to prevent misrepresentation of the entity. With many common domain names already taken up, new businesses have to settle for near-matches.
Uniform Resource Locator (URL)
The World Wide Web is a collection of hypermedia (text, images, videos, and content in other formats that link to each other). These hypermedia elements are referred to as resources. To identify a specific resource, web browsers use what is known as a Uniform Resource Locator (URL). A typical URL will have the form http://www.example.com/resource.html , which includes the protocol to be used to access the resource (HTTP), the domain name that identifies the server on which the resource is located (www.example.com ), and finally, the resource name (resource.html).
