All devices on the World Wide Web are identified by a unique number called an IP address, such as 123.123.123.123. If you have a website, the domain that you type in order to load it is to save you time, however the server where the website files are still has an IP. Because there're far more websites and devices than there're IP addresses, all shared hosting servers have a number of sites under the very same IP, while when you use a dedicated server you will have a dedicated IP as well. Even in the first case though, you can obtain a dedicated IP for your websites and host them on a shared server. An advantage would be that you may get far better search engine rankings as a dedicated IP often means a quicker loading site. What is more, you need such an IP when you would like to get an SSL certificate for your site and protect the info that your visitors submit on it.