A domain name is the address people type into a browser URL to reach a site. Domain names exist to make it easier for people instead of memorising number like 192.168.1.1 for every single website you want to visit. Each domain name is unique to a specific website and cannot be shared or duplicated with other web pages. If you look at the very top of a webpage, you’ll see the domain name of a website.
There are different types of domain names with many different extensions. The most popular extension is .com but there are others such as .net .org .info .
There are different categories of top-level domains extensions: country code and sponsored domains. Country codes are country-specific for example, .uk is for the United Kingdom. Sponsored domains have a sponsor representing a specific community for example, .edu is for education-related organisations and .gov are for government sites.
A subdomain is a child domain under the main name, for example, if you wanted a store for the website www.silvertoad.co.uk it may be listed with the subdomain store.silvertoad.co.uk. When you register your domain you have permission to create subdomains for it yourself.