–see http://helpdesk.bluehost.com/index.php/kb/article/1 for more info on nameservers updates.

Nameservers are required to host your website on the Internet. They are part of the Domain Name System (DNS for short) the name translation system that converts names into numbers (Internet Protocol Addresses – IP)  that allows computers to communicate with each other. So when you type in the domain name example.com in the address bar of your favorite browser (mine is Firefox) and hit enter, the browser starts the name lookup process. If there is no cached version to the nearest ISP servers, or the one that you have setup when you were connecting to the Internet, parent nameservers are asked for the domain name. These authorative nameservers respond who is responsible for this domain name (primary and secondary nameserver information – in your case it would be the bluehost servers since you host the domain there). After receiving this information the browser asks the nameservers for the IP address and connects to this IP address requesting the website. Then the servers responds with web site data and the browser displays the website page.