All devices on the Internet are recognized by a special number called an IP address, for instance 220.127.116.11. If you have a site, the domain name that you type to be able to access it is to save you time, but the server where the site files are still has an IP address. Because there are far more sites and devices than there are IPs, all of the shared web hosting servers have a number of websites under the same IP, whereas with a dedicated server you'll be given a dedicated IP as well. Even in the first case though, you're able to acquire a dedicated IP for your websites and host them on a shared server. One benefit would be that you may get better search engine positions since a dedicated IP generally means a quicker loading site. In addition, you need such an IP if you plan to buy an SSL certificate for your site and protect the data that visitors submit on it.