All devices on the World Wide Web are identified by a special number called an IP address, for example 126.96.36.199. When you have a site, the domain name that you enter to open it is for your convenience, however the server where the site files are still has an IP address. As there are a lot more sites and devices than there're IP addresses, all the shared web hosting servers have a number of websites under an identical IP, while with a dedicated server you'll get a dedicated IP too. Even in the first case though, you'll be able to obtain a dedicated IP for your sites and host them on a shared server. One advantage would be that you'll get superior search engine rankings since a dedicated IP usually means a quicker loading website. In addition, you need such an IP in case you want to buy an SSL certificate for your website and shield the information that visitors submit on it.