All devices on the Internet are recognized by a specific number called an IP address, for instance 126.96.36.199. When you have a site, the domain name that you type in order to access it is to save you time, but the server where your website files are still has an IP address. Since there are far more websites and devices than there are IP addresses, all shared website hosting servers have a number of websites under the very same IP, whereas when you use a dedicated server you will have a dedicated IP too. Even in the first case though, you're able to get a dedicated IP for your websites and host them on a shared server. One advantage would be that you may enjoy better search engine rankings because a dedicated IP often means a faster loading website. Also, you need such an IP when you intend to purchase an SSL certificate for your website and protect the data that visitors submit on it.