All devices on the World Wide Web are recognized by a special number called an IP address, for instance 18.104.22.168. In case you have a site, the domain name that you type to be able to access it is to save you time, but the server where the website files are still has an IP. Considering that there are a lot more websites and devices than there are IP addresses, all of the shared hosting servers have a number of sites under the same IP, whereas when you use a dedicated server you will have a dedicated IP too. Even in the first case though, you can acquire a dedicated IP for your sites and host them on a shared server. An advantage would be that you will get better search engine positions because a dedicated IP usually means a quicker loading site. What's more, you need such an IP in case you plan to purchase an SSL certificate for your website and secure the data that your visitors submit on it.