All devices on the Internet are recognized by a specific number called an IP address, for example 220.127.116.11. If you have a site, the domain name that you enter to be able to access it is to save you time, but the server where your site files are still has an IP address. Due to the fact that there're a lot more websites and devices than there're IP addresses, all of the shared website hosting servers have a number of sites under an identical IP, whereas using a dedicated server you'll have a dedicated IP as well. Even in the first case though, you're able to acquire a dedicated IP for your websites and host them on a shared server. One advantage would be that you may get improved search engine rankings as a dedicated IP generally means a quicker loading site. Also, you need such an IP if you intend to acquire an SSL certificate for your site and secure the data that your visitors submit on it.