All devices on the Internet are identified by a special number called an IP address, for instance 220.127.116.11. If you have a site, the domain that you type in order to open it is for your convenience, however the server where the site files are still has an IP address. Considering that there are far more websites and devices than there are IP addresses, all shared website hosting servers have a number of websites under the very same IP, whereas with a dedicated server you'll have a dedicated IP too. Even in the first case though, you are able to obtain a dedicated IP for your sites and host them on a shared server. One advantage would be that you may have far better search engine rankings because a dedicated IP often means a faster loading site. What is more, you need such an IP if you would like to obtain an SSL certificate for your website and secure the data that your visitors submit on it.