Welcome, Dear.

It seems you want some useful and informative knowledge about URL, domain name definition, and some examples to clear your concepts.

Certainly, you are quite lucky because you are now at the best place.

What is a Domain Name System Definition?

This system came in 1980.
It is a system by which first the websites are assigned names, and furthermore, the user need not type the IP address to access a site.
Consequently, they give names to identify any site online.
This system is in connection with a network.

Have a look at this brilliant infographic about Working of DNS Server.

Internet Domain Name Definition, Meaning, and Examples:

It is a name that works in identifying an IP address.

The IP address is not by users. However, they use the domain to visit any web page, they are registered with DNS and are use URL for locating a website.

Some examples are

google.com
zappedia.com

Levels of the Domain:

They have the suffix that categorizes them in different levels.
There is the top, second and third level of them.
Above all, each one has its importance and use.

What is the Top-Level Domain?

It is at the top position in the DNS. Particular organizations manage them and it is further classified into:

1) Generic Top-Level Domain Name Definition:

They are the ones that have 3 or more characters in the suffix.

2) Sponsored TLD:

Private companies sponsor them, and such companies have their rules and regulations that people should follow.

3) International Country Code TLD:

They are specially chosen to represent any particular country.
Mostly have 2 characters.
For example .uk.
They were introduced in 2009 and contained an encoded part that accounts for a specific country.
The encrypted part is in the native language of the country that is being represented by that it.

4) Brand TLD:

In contrast, they are used for branding and mostly consist of a company name.

For example:

.google
.gmail

List of Examples of Top-Level Domains:

Some of them are:

.com( They are used for commercial purposes)
.org ( for organizations)
.edu ( for educational institutions)
.gov ( used by governments)

Some country code TLD are:

.int ( employed by international companies)
.br (operated by Brazil)
.ng( for Nigeria)
.th (for Thailand)

Second Level Domain:

The second level is the one that appears just before the TLD.

Most importantly, this part is immediately on the left side after the dot.

Let me explain with some examples.

In googel.com, .com is TLD while Google is the second level
In ABC.uk, .uk is TLD while ABC (below the dot) is the second tier.

In other words, they usually represent the organization that has registered with any TLD.

For example, an organization LMN would register a domain with LMN.com so in the second level domain their is the name or identity of the organization.

Third-Level Domain:

These are the one on the left side of the second tier.
For example in www.google.com, www is a third level domain.

There can be a 4^th and 6^th level of them also.

Most importantly, there is no restriction.

The fourth and fifth level will be on the left side of the dot of the third level.

Domain Name Rules:

Specific standards and regulations are followed on registering these names.

Some of them are:

Firstly, the name should not be too long, and it should be in such a way that people remember it quickly.
Secondly, spell them correctly.
Further, if there are multiple words, try to make them clear by use of hyphens.
Moreover, choose the one that is easily pronounceable.
In addition, if the name you are searching for has already been registered, you can try using the name with some modifications or appending something before or after it.

Characters Allowed in Domain Names:

It can have letters from A-Z, hyphens, numbers (from 0 to 9), underscores and some punctuation.
You can’t use spaces and keep in mind not to start or end it with hyphens.
However, hyphens and underscores are used in between as separators.

Are Domain Names Case Sensitive?

You don’t need to be case conscious, i.e., they are both cases sensitive.
In short, you write abc.com or ABC.com both will result in the same site.

Domain Name vs. URL:

URL stands for uniform resource locator.
Domain name is a part of URL.
It is the name of the actual site while URL is the address of a website or any page.
URL is the path to any page.
Most of the URL has www in starting. It uses HTTP, i.e., hypertext transfer protocol. They are extensions

What is a Website Address?

It is the URL of a website.
Through your web address, you are visible on the internet, and people find you quickly.

What is a Computer With a Domain Name Called?

In this case, it is a group of computers that are on the same network.

Meanwhile, they share the resources.

For instance,

Computers in a library/lab of any educational institution.
Computers in an office

Website Hosting:

You want your site to be online and know how to buy a domain name too.

Now, what would be your next step?

Firstly, it would be the web hosting registration. Web hosting is a technology by which users can put their website online.

It provides accommodation for websites.

This is to say; these services are provided by hosting companies. Some are free, however, on the hand, you will need to pay an amount for some.

Google web hosting is an example of an impressive free hosting service.

To sum up, hosting companies have their server. There are shared hosting also.

How to Create a Virtual Host in Xampp?

You can also host websites on Xampp. It is a web server package.

To do this:

Download and then install it
Then in the htdocs folder copy the PHP files you want to test on the server.
In your browser run the PHP files. For example, if your file xyz.php is in .htdocs then in your browser type localhost/xyx.php to run it.

If you what is SQL server and its working then you can easily do the database work too.

Useful Read: Know What is Apache Web Server and HTTPD