All devices on the Internet are identified by a special number called an IP address, for instance 126.96.36.199. If you have a website, the domain that you enter to access it is to save you time, yet the server where your website files are still has an IP address. Considering that there are far more websites and devices than there are IPs, all shared web hosting servers have a number of sites 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 can get a dedicated IP for your sites and host them on a shared server. An advantage would be that you may have better search engine rankings as a dedicated IP often means a faster loading site. Also, you need such an IP when you plan to obtain an SSL certificate for your site and shield the info that visitors submit on it.