WWW is the abbreviation for the World Wide Web. In the early days of the internet, some experts started using it to indicate that it is a web address.
However, it is not a requirement, and most websites don’t use www in their website addresses anymore.
Technically, www is a subdomain of your main domain name. Anything that comes before your main domain and is followed by a dot is considered a subdomain like videos.wpbeginner.com.