All devices on the Web are identified by a unique number called an IP address, for instance 18.104.22.168. When you have a site, the domain name that you enter to open it is for your convenience, however the server where the site files are still has an IP. Because there're a lot more sites and devices than there're IPs, all the shared website hosting servers have a number of websites under the same IP, while when you use a dedicated server you'll have a dedicated IP as well. Even in the first case though, you will be able to acquire a dedicated IP for your websites and host them on a shared server. One advantage would be that you may enjoy improved search engine rankings since a dedicated IP generally means a faster loading website. Furthermore, you need such an IP when you intend to get an SSL certificate for your website and shield the info that visitors submit on it.