NS Records or Name Server Records are kept by the Registrar. The NS Records tell a browser where the DNS Records are being held within the internet. So in other words, NS Records are like street signs found on highways.
DNS Records on the other hand are like a bunch of street signs relating to a Domain. Since a Domain is basically space. It can hold things like files, a website, and even Emails. So it's only natural that you'd have signs to direct traffic to these things.