All devices on the Internet are recognized by a specific number called an IP address, for example 123.123.123.123. When you have a website, the domain that you type to open it is for your convenience, however the server where the site files are still has an IP address. Because there're many more sites and devices than there are IP addresses, all the shared hosting servers have a number of sites under the same IP, whereas with a dedicated server you'll get 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. One benefit would be that you will have improved search engine positions since a dedicated IP generally means a faster loading site. Also, you need such an IP when you would like to buy an SSL certificate for your site and protect the information that visitors submit on it.