You've purchased a Website name also called a Domain Name, set up hosting then uploaded your website.

Then you go to your registered and point your domain name to your hosting space and nothing happens. nothing,nada,zip, bupkis. Why?

DNS(Domain Name Server) propagation (The process of spreading to a larger area) thats why!

How's that work then

How DNS works. When you set up your website your host creates a, lets call it a file called a DNS Record. Your domain registrar (goddady, register.com .etc) redirects to your host as the place your website is(DNS authority).

To find your website they first must go to the registration database to find out who the DNS authority is for your website. Then go to the host to find out what the IP Address(the actual numbered address for your site) is for your domain name, and from there your visitors can now view your website.

What a Pain!

To make matters worse to speed up the rate at which their customers can view the internet, each Internet Server Provider makes a copy of the master DNS record instead of looking them up on the Internet each time someone wants view a website.

Sure it speeds things up but now it take a long time for your website to be visible to everyone.

This is of course an over simplified explanation to make it easy to understand.

Tools to help:

http://www.whatsmydns.net

http://www.dnsgoodies.com/

http://code.google.com/speed/public-dns/