Name Servers are the part of the internet which hold the records about the addresses for your Domain Name. Because of this, they are very important, and should only be controlled by someone with knowledge about the effects changes have. Name Servers are just computers, running a special program (or 'service') which responds to requests for conversion of domain names into IP Addresses.
When someone types your Domain Name into a web browser (i.e. www.goldhosts.com), this needs to be turned into an IP Address so that your computer knows which computer (or 'server') on the internet hosts your web site. The same is true for your email. When an email is sent to you, the Name Servers are asked which computer it should be sent to.
This information is held on Name Servers. The records held on Name servers include 'A Records', which are direct conversion into IP Addresses, and also 'MX Records', which list other A Records for handling email. There can be more than 1 MX record, with different priorities, so that backup email servers can be available in the event of failure.
Each domain name should have at least 3 Name Servers. Some providers only use 2. With knowledge like this which Goldhosts have proved invaluable when something does go wrong.
Name Servers normally issue answers with a 'life expectancy'. This means an answer can be held as true for quite some time. For this reason, changes to Name Servers can take up to 48 hours to 'propagate' across the whole internet.
To ensure your Name Servers, are dealt with properly, make sure your Domains are with GoldHosts.