What do you mean by "speed"
Evidently the speed of the nameserver will change the "speed" that a site gets resolved and then loads?
A name server is the DNS server that holds the A records, MX records etc..
So when you browse to lets say, Google.com
Your browser searches for the Nameserver on google.
It then queries the nameserver for the A record of the domain google.com
Your browser then connects to the IP in the A record.
Nameserver = yellow pages.
A record = a telephone number for a business inside the yellow pages..