All devices on the Internet are recognized by a specific number called an IP address, for instance 126.96.36.199. In case you have a website, the domain that you type to load it is to save you time, however the server where your site files are still has an IP. As there are far more websites and devices than there are IP addresses, all 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 as well. Even in the first case though, you can get a dedicated IP for your sites and host them on a shared server. An advantage would be that you may get far better search engine positions as a dedicated IP generally means a quicker loading site. What is more, you need such an IP when you plan to acquire an SSL certificate for your website and shield the data that visitors submit on it.