All devices on the World Wide Web are identified by a specific number called an IP address, for instance 188.8.131.52. When you have a site, the domain name that you enter in order to open it is to save you time, however the server where your website files are still has an IP address. Since there are many more sites and devices than there're IPs, all of the shared web hosting servers have a number of sites under an identical IP, while with a dedicated server you'll get a dedicated IP too. Even in the first case though, you can acquire a dedicated IP for your websites and host them on a shared server. An advantage would be that you may have superior search engine rankings as a dedicated IP often means a quicker loading site. What's more, you need such an IP in case you intend to obtain an SSL certificate for your website and protect the information that your visitors submit on it.