All devices on the World Wide Web are recognized by a special number called an IP address, such as 220.127.116.11. If you have a site, the domain that you type to open it is to save you time, but the server where your site files are still has an IP. Since there're many more sites and devices than there are IP addresses, all of the shared website hosting servers have a number of websites under the very same IP, whereas using a dedicated server you will have a dedicated IP as well. Even in the first case though, you can obtain a dedicated IP for your sites and host them on a shared server. An advantage would be that you'll have improved search engine rankings because a dedicated IP usually means a faster loading website. Last but not least, you need such an IP in case you plan to buy an SSL certificate for your website and shield the information that visitors submit on it.