Child domain vs domain

Can you tell me what would be the difference and if there are any pros / cons of each method, between

a. creating a website with the domain sub.domain.com
b. creating a domain of domain.com and then creating a child domain of sub?

This is purely from an educational perspective. Also I have always known these as sub domains or addon domains (cPanel) rather than child. Any reason they are not called sub domains?

many thanks

@daniel

There is no physical difference between them if you create sub.domain.com as a website in CyberPanel or child domain they are treated similarly.

But if you have multiple users, a website can be owned by a user and its child domains belong to the same user. However if you also create child-domain as a website, you can assign a different owner to it.

Apart from that function wise, they are treated similarly.

Thanks for the clarification