All devices on the Internet are recognized by a special number called an IP address, for example 123.123.123.123. In case you have a site, the domain name that you type in order to load it is for your convenience, but the server where your site files are still has an IP. Because there are far more sites and devices than there're IP addresses, all shared web hosting servers have a number of sites under an identical IP, whereas with a dedicated server you'll get a dedicated IP too. Even in the first case though, you can acquire a dedicated IP for your sites and host them on a shared server. One advantage would be that you may enjoy better search engine rankings as a dedicated IP usually means a faster loading website. What's more, you need such an IP in case you intend to obtain an SSL certificate for your website and secure the info that visitors submit on it.