All devices on the Web are recognized by a special number called an IP address, for instance 123.123.123.123. If you have a website, the domain that you type in order to open it is for your convenience, but the server where the site files are still has an IP. As there're many more websites and devices than there're IP addresses, all shared website hosting servers have a number of websites under the very same IP, while using a dedicated server you'll have a dedicated IP as well. Even in the first case though, you are able to obtain a dedicated IP for your websites and host them on a shared server. An advantage would be that you may have far better search engine positions since a dedicated IP generally means a faster loading website. Last but not least, you need such an IP if you plan to obtain an SSL certificate for your site and shield the data that your visitors submit on it.