All devices on the World Wide Web are recognized by a special number called an IP address, for instance 220.127.116.11. When you have a site, the domain that you enter to access it is for your convenience, but the server where your site files are still has an IP address. Since there are far more sites and devices than there're IP addresses, all shared hosting servers have a number of sites under an identical IP, while with a dedicated server you will have a dedicated IP as well. Even in the first case though, you will be able to obtain a dedicated IP for your websites and host them on a shared server. An advantage would be that you will enjoy superior search engine rankings since a dedicated IP often means a quicker loading site. In addition, you need such an IP in case you want to purchase an SSL certificate for your site and secure the info that your visitors submit on it.