All devices on the Web are recognized by a specific number called an IP address, for instance 220.127.116.11. If you have a website, the domain that you enter to access it is for your convenience, however the server where your website files are still has an IP address. As there're a lot more sites and devices than there're IP addresses, all shared web hosting servers have a number of websites under an identical IP, whereas using a dedicated server you'll have a dedicated IP too. Even in the first case though, you will be able to acquire a dedicated IP for your sites and host them on a shared server. One advantage would be that you will get improved search engine positions since a dedicated IP usually means a faster loading site. Last but not least, you need such an IP when you would like to purchase an SSL certificate for your site and shield the information that visitors submit on it.