You would have one Apple Account that is used for registering Apple products and linking Apple services, including getting apps from the App Store.
Additional accounts would be separate from that, and not linked to the first Apple Account. Using more than one account would make your Apple life very difficult and some things may be impossible. If you want a different Apple Account name, then you can change it within the first Apple Account properties. For most cases and users, it would be undesirable to use a completely new account.
The new account creation can be quite useful for a next user of that Apple device, if you were to sell it or give it away.
“Creating accounts for other apps” could be totally unrelated to this. Apps can optionally use any kind of separate type of account specific to their services. It depends on the app.