All devices on the Web are identified by a special number called an IP address, for instance 22.214.171.124. When you have a site, the domain that you enter to load it is to save you time, but the server where your site files are still has an IP. Due to the fact that there're a lot more websites and devices than there are IP addresses, all shared hosting servers have a number of websites under an identical IP, while using a dedicated server you'll get a dedicated IP as well. Even in the first case though, you will be able to obtain a dedicated IP for your sites and host them on a shared server. One advantage would be that you'll enjoy improved search engine positions since a dedicated IP usually means a faster loading site. In addition, you need such an IP in case you plan to get an SSL certificate for your website and shield the information that your visitors submit on it.