All devices on the Web are identified by a specific number called an IP address, such as 220.127.116.11. When you have a website, the domain name that you enter to be able to access it is to save you time, yet the server where the site files are still has an IP. Considering that there're far more sites and devices than there're IP addresses, all of the shared website hosting servers have a number of websites under the very same IP, while with a dedicated server you'll have a dedicated IP as well. Even in the first case though, you can get a dedicated IP for your websites and host them on a shared server. One advantage would be that you will get improved search engine rankings because a dedicated IP often means a faster loading website. In addition, you need such an IP if you plan to obtain an SSL certificate for your website and protect the data that visitors submit on it.