What causes some websites to include 'www' in their URL, while others leave it out?

A typical website URL might look like this: https://www.Mytour.com. However, you may have noticed that many sites do not require the 'www' part. You can simply use https://Mytour.com to access Mytour. Additionally, some websites have different naming conventions, such as http://www.delphion.com and http://journal.iftech.com, where a different term is used to refer to the site. Another example would be a name like ftp.microsoft.com, which can either be used in the FTP command or entered as a URL in a browser (ftp://ftp.microsoft.com).

If you've read the article How Web Servers Work, you're familiar with name servers and IP addresses. A name server maps a domain name to an IP address. When you enter a URL like https://www.Mytour.com in your browser, it reaches out to the default name server and inquires, 'Do you know about www.Mytour.com?' If it's a new query, the name server will reach out to the .com domain server and ask if it can locate the server for Mytour.com. Once the name server for Mytour.com is found, it will check if it has a record for www.Mytour.com and return the associated IP address for the browser to connect to.

The network administrator for the domain 'Mytour.com' is responsible for assigning specific names within the domain to machines and their corresponding IP addresses. In larger companies, separate machines (with different IP addresses) handle different types of traffic such as WWW, FTP, Telnet, and more. In smaller websites, a single machine may manage all types of traffic.

The network administrator creates a list of domain names and their corresponding IP addresses, like this:

The administrator has the freedom to add any names to that list, as name servers do not impose restrictions. For instance, the administrator could add scooby.Mytour.com, scooby.doo.Mytour.com, or even scooby.dooby.doo.Mytour.com, and when someone types any of those names, the name server will return the associated IP addresses.

For websites that function without the 'www' prefix, it simply indicates that the administrator has configured the system so that when no prefix is provided, the name server returns the IP address for the web server directly.