All devices on the Internet are recognized by a special number called an IP address, for instance 123.123.123.123. If you have a site, the domain name that you enter to be able to load it is for your convenience, but the server where your website files are still has an IP. Since there are far more sites and devices than there're IP addresses, all of the shared website hosting servers have a number of websites under the very same IP, while with a dedicated server you'll be given a dedicated IP too. 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 benefit would be that you'll have superior search engine rankings as a dedicated IP often means a quicker loading website. What is more, you need such an IP if you would like to obtain an SSL certificate for your site and secure the data that your visitors submit on it.