All devices on the World Wide Web are identified by a unique number called an IP address, such as 123.123.123.123. When you have a site, the domain that you enter to be able to load it is to save you time, yet the server where your website files are still has an IP address. Because there're far more sites and devices than there're IPs, all shared website hosting servers have a number of sites under an identical IP, while with a dedicated server you will have a dedicated IP too. Even in the first case though, you can obtain a dedicated IP for your websites and host them on a shared server. One advantage would be that you'll get improved search engine rankings as a dedicated IP often means a faster loading site. Furthermore, you need such an IP if you would like to get an SSL certificate for your site and protect the info that visitors submit on it.