This article from UK2.NET is a guide to add-on domains, their function and how to tell if your account includes add-on domains as part of your hosting package.
Some shared hosting plans from UK2.NET allow for the creation and hosting of multiple websites on a single account. These secondary domains are referred to as “add-on domains”, because they do not require their own shared hosting account and are usually attached to your original domain.
You will see the “Addon Domains” tab on your control panel within the “shared hosting” tab if your hosting plan allows for the hosting of addon domains:
If you would like to purchase a hosting plan with that allows for add-on domains, please refer to the “Website” section when selecting a shared hosting plan. Your options range from one single website to an unlimited number of add-on domains.
If you would like additional help linking add-on domains to your UK2.NET shared hosting account, click here