Name servers of devpilot.us.

The NS records name the servers that hold a domain's records. The copy that counts is the one at the registry, which you set at your registrar; the domain's own NS records should list the same servers. When the two disagree, some resolvers follow one and some the other, and changes seem to work only half the time.

You change name servers at the registrar where the domain is registered, not at the DNS host. Copy every record to the new DNS host first, then switch. Resolvers keep the old name servers until their cached copy expires, which can take a day or two, so leave the old DNS host running in the meantime.

The DNS standard requires every zone to be served by at least two name servers, and the guidance for secondary servers asks that they not share one network or location. If every name server sits behind one provider, an outage there takes the domain offline.

• Primary server and contact: the first dot of the contact is the @, so dns-admin.google.com means dns-admin@google.com.
• Serial: goes up with every change. Many hosts write it as a date, such as 2026101001.
• Refresh, retry, expire: how secondary servers keep their copy current, and when they stop answering if the primary is gone.
• Negative TTL: how long resolvers remember that a name does not exist. A new subdomain can stay invisible that long to anyone who looked for it before it existed.

A domain on the name servers of a marketplace or parking service (Atom, Afternic, Sedo, Dan.com, Bodis and others) usually shows a "for sale" page or ads. That is the clearest public sign that the owner would sell it.