All devices on the Web are recognized by a unique number called an IP address, for instance 188.8.131.52. In case you have a website, the domain name that you enter to be able to load it is for your convenience, however the server where the website files are still has an IP. Considering that there're many more websites and devices than there are IP addresses, all the shared website hosting servers have a number of websites under the very same IP, while with a dedicated server you'll get a dedicated IP too. Even in the first case though, you're able to acquire a dedicated IP for your sites and host them on a shared server. One advantage would be that you may have superior search engine positions since a dedicated IP generally means a faster loading website. Last but not least, you need such an IP in case you intend to acquire an SSL certificate for your site and secure the info that visitors submit on it.