There are 2 aspects to any DNS function: delegation and nameserver records.

Delegation simply means the list of servers (called nameservers) that carry the DNS information for this domain name. This is only a list of the servers responsible, as the technical functioning of the domain is not handled by the registrar.

The nameservers listed in the delegation of the domain name carry the actual DNS information (called zone files) for the domain name and can be located anywhere on the internet. This kind of DNS handles the standard domain name to IP address translation (where the website for this domain name is, which server handles email for the domain name, etc...).