What is DNS and how do I point it to a particular web server?

DNS means Domain Name Server.

When you own a domain name such as www.whatever.com, you own a name that has a subsequent pointer to a computer (server) on the Internet that runs your site.

Go to www.betterwhois.com and type in your domain address. The results will tell you several things.

The Registrar is the online company where your domain name is managed. If your Registrar is GODADDY.COM INC, you need to log into your Godaddy account to manage your DNS and/or renew your domain name.

The Nameserver tells you the name of the server (your site has to live somewhere) might read something like: ns1.whateverwebserver.com and ns2.whateverwebserver.com

So at some point, your web developer/designer will need to ask you to please "point the DNS" to the new server where your site will live, for example:
ns1.supercleanengine.com
ns2.supercleanengine.com

This can be easily done though your godaddy account or whatever Registrar you use. Sometimes people have trouble with this because they have lost track of their login/account info and just know they only get billed ever 24 months. This is a reminder that it's very important to have control over your domain name, because that is essentially YOUR NAME in cyberspace. Lose that, and how do people find you?

I have seen countless people have trouble with regaining control of their DNS because they a) bought it through yahoo!; or b) they bought domain name privacy when they registered their domain, forcing them to have to un-peel another layer of account control (and lost passwords) in order to change the DNS thereby getting control of where your website will live.

If you can't point your name to the proper server, you don't have control over your website.

Below are 2 screen grabs of the Godaddy.com interface for changing your DNS.