All devices on the World Wide Web are identified by a unique number called an IP address, for instance 220.127.116.11. In case you have a site, the domain name that you type to load it is for your convenience, but the server where the site files are still has an IP. Because there are a lot more websites and devices than there're IP addresses, all shared website hosting servers have a number of sites under an identical IP, while with a dedicated server you'll be given a dedicated IP as well. Even in the first case though, you can acquire a dedicated IP for your sites and host them on a shared server. One benefit would be that you will have better search engine rankings as a dedicated IP generally means a quicker loading site. Last but not least, you need such an IP when you want to purchase an SSL certificate for your site and protect the information that visitors submit on it.