An addon domain is an additional domain that the system stores as a subdomain of your main site. Use addon domains to host additional domains on your account. For more information, read the official documentation here: https://go.cpanel.net/AddonDomain
In simple words, by using Addon domains, you can host multiple websites using same CPanel web hosting. All our Hybrid Web Hosting plans come with unlimited addon domains. It means, as long as your web hosting space can accommodate, you can host as many domains as you want.
When you create an addon domain name, you are specifying the CPanel and server that you are going to point another domain to same server and on a new public_html location for the domain.
This means, same web hosting account can hold multiple websites this way, and you can manage all the websites using the same control panel easily.
Best security practices to follow when hosting multiple websites.
a) Never use the folder names as domain names, it means, when you create a new addon domain in cpanel, by default it will create a new directory with name same as domain name. So, make sure that you customize it and not to use default names.
b) Always turn off directory indexing for all the domains and addon domains, hosted on the server.
c) Keep note of which is the directory for a addon domain and try to use some sort of documentation for reference purpose in future.
You must always point the newly added domains to our servers, in the same manner you pointed the primary domain name.
Watch this video to learn how to create addon domains in your account.