All devices on the Web are identified by a specific number called an IP address, such as 126.96.36.199. In case you have a site, the domain name that you enter in order to load it is for your convenience, however the server where the website files are still has an IP. Considering that there're far more sites and devices than there are IP addresses, all of the shared web hosting servers have a number of websites under an identical IP, while when you use a dedicated server you'll get a dedicated IP too. Even in the first case though, you are able to obtain a dedicated IP for your websites and host them on a shared server. One advantage would be that you will enjoy improved search engine positions since a dedicated IP usually means a faster loading site. In addition, you need such an IP in case you would like to purchase an SSL certificate for your site and secure the data that visitors submit on it.