Name Servers are classified into two categories as Custom Name Server & Private Name Server/Child Name Server. Custom Name Server will be common for all the accounts under a server which will be having the domain name of hosting company with the prefix as ns followed by a number. Private Name Server/ Child Name Server will be the same as of domain name. For example: If your domain name is example.com then your private name server will be ns1.example.com & ns2.example.com. So it will be unique for each domain and it shows the difference for the bots.