All devices on the World Wide Web are identified by a specific number called an IP address, such as 184.108.40.206. When you have a site, the domain that you type in order to access it is for your convenience, however the server where the site files are still has an IP. Because there are far more websites and devices than there're IPs, all of the shared web hosting servers have a number of websites under the same IP, whereas using a dedicated server you'll have a dedicated IP as well. Even in the first case though, you'll be able to obtain a dedicated IP for your sites and host them on a shared server. One benefit would be that you will have far better search engine positions as a dedicated IP generally means a faster loading website. Also, you need such an IP if you plan to obtain an SSL certificate for your website and shield the information that your visitors submit on it.