The whole category in one page.
THE DISTINCTION
Addon domain and subdomain: separate content, separate directory.
Alias: the same content at another name.
FOR A SECOND BUSINESS
An addon domain, or a separate account if it is a client site.
FOR A SECTION OF YOUR SITE
A subdirectory, which shares search authority.
A subdomain only where the content is genuinely separate.
FOR A DEFENSIVE REGISTRATION
An alias, redirected permanently to your main domain.
Serving identical content at two addresses splits ranking.
AFTER ADDING ANY DOMAIN
Run AutoSSL. That step is the most commonly forgotten.
IF YOUR DNS IS EXTERNAL
Creating a subdomain in cPanel does not make it resolve.
The record must exist where your DNS actually lives.
FOR STAGING
Protect it with Directory Privacy before putting anything in it.
Never copy a staging database over a live site with real data.
WHEN REMOVING A DOMAIN
Remove the files and database too.
An abandoned application is the most common route of compromise.
