A domain, or more commonly referred to as a domain name, is essentially the URL of a webpage.
However, domains are used to make IP addresses more easy to memorise and use.
For example, it is much easier to open cbronline.com than 567.432.123.342/mysite. Here cbronline.com is the domain name.
Every domain name is followed by a suffix that either shows the country where the website is based and/or intended to. This is known as top level domain, which can also take the form a gov, edu, org and so on.