This article provides you with information on different domain types.
Addon domains are completely different domains that are added to a cPanel account. Their main purpose is to host multiple websites on a single cPanel account, and can also be used for email. Although they are connected to the same cPanel account as the main domain, to anyone who visits the website or sends an email for an addon domain the main/addon domains are completely transparent from and don't look linked to each other in any way.
They share the CPU/RAM/Disk Space of your cPanel account. You can create individual subdomains for addon domains just as you can a normal domain.
INFO: For steps to add an addon domain to you cPanel please see this guide here.
Subdomains are "branches of an existing domain", for example, cpanel.yourdomain.co.za , webmail.yourdomain.co.za. They are used to host different pages that are connected to your main domain name. You are also able to set the A record for a subdomain to another server if you wish. They also share the CPU/RAM/Disk Space of your cPanel account.
INFO: For steps to add a sudomain domain to you cPanel please see this guide here.
These domains are like Addon domains however they can't be used to make a new website. By default when you go to a domain that's parked as an alias it will go to the website of the main cPanel account.They also share the CPU/RAM/Disk Space of your cPanel account
INFO: For steps to add an domain alias to you cPanel please see this guide here.
Below Is a table that shows what the three types of domains are capable of.