Addon Domains create create subdomains, as this is how cPanel handles the creation of Addon Domains. An addon domain is technically a parked domain on the subdomain that is created, when looking at it in reference to Apache VirtualHost entries. The addons work and function like subdomains but to all those looking in from the outside (your visitors) they appear as separate domains.
Addon Domains will not have their own cPanel, but you’re able to use redirects, Softaculous, create email accounts, subdomains, etc. for them right there in your main cPanel account. Just as you do for your main domain on the account.
For example, if you were to go Softaculous and choose WordPress, it will show you a list of WordPress installations. There would also be an Install Now button. After clicking that, you’d choose the addon domain and directory you want to install to. Just as you could for your main domain.
You can find a list of your Addon Domains in your cPanel by going to Home > Domains > Addon Domains