Hostgator Nameservers address information is sent in your welcome e-mail when your hostgator account is created. Usually this is within 30 minutes after you signup with them. The nameservers should look like:
nsxxx.hostgator.com
nsxxx.hostgator.com
Where xxx are numbers.If you don’t get them in your welcome email or you have deleted that email contact the support.
Namerservers
Nameservers are required in order your site to be live. Since every computer connected to the Internet (including any servers) requires unique IP address (at the moment of connecting and while is connected). Because IPs are hard to remember (they are numbers) people have invented the DNS (Domain Name System). When you want to visit some site, the browser in background uses DNS to find where the server is. Once it founds it, it connects to it. Nameservers are part of this system and are used to resolve the domain names to their respective IP addresses. At least two name servers are required in case one of them fails the other one will be the backup. They are entered at your domain name registrar.