All devices on the World Wide Web are identified by a specific number called an IP address, such as 18.104.22.168. If you have a website, the domain name that you enter to load it is to save you time, but the server where the site files are still has an IP. Considering that there are a lot more websites and devices than there're IPs, all shared website hosting servers have a number of websites under the same IP, while with a dedicated server you will have 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. One advantage would be that you'll enjoy far better search engine rankings because a dedicated IP often means a quicker loading website. Also, you need such an IP in case you intend to buy an SSL certificate for your website and secure the info that visitors submit on it.