All devices on the World Wide Web are identified by a special number called an IP address, for instance 22.214.171.124. If you have a website, the domain that you enter to access it is for your convenience, however the server where the site files are still has an IP. Since there are a lot more sites and devices than there are IP addresses, all of the shared web hosting servers have a number of sites under the same IP, while using a dedicated server you'll be given a dedicated IP as well. Even in the first case though, you are able to acquire a dedicated IP for your sites and host them on a shared server. An advantage would be that you will have better search engine rankings as a dedicated IP usually means a faster loading website. In addition, you need such an IP when you plan to get an SSL certificate for your website and shield the information that your visitors submit on it.