All devices on the World Wide Web are recognized by a specific number called an IP address, such as 123.123.123.123. When you have a site, the domain name that you enter to be able to open it is to save you time, yet the server where your website files are still has an IP. As there're many more sites and devices than there're IPs, all the shared hosting servers have a number of sites under the same IP, whereas using a dedicated server you'll have a dedicated IP too. Even in the first case though, you can get a dedicated IP for your websites and host them on a shared server. One benefit would be that you will enjoy better search engine positions as a dedicated IP often means a quicker loading site. Last but not least, you need such an IP when you would like to purchase an SSL certificate for your website and secure the info that your visitors submit on it.