All devices on the Internet are recognized by a special number called an IP address, for example 123.123.123.123. When you have a site, the domain name that you enter in order to load it is to save you time, however the server where your site files are still has an IP address. Since there're far more websites and devices than there're IP addresses, all the shared website hosting servers have a number of sites under the very same IP, whereas with a dedicated server you'll be given a dedicated IP as well. Even in the first case though, you will be able to get a dedicated IP for your websites and host them on a shared server. One benefit would be that you'll have better search engine rankings as a dedicated IP usually means a faster loading website. What is more, you need such an IP if you would like to get an SSL certificate for your site and protect the data that visitors submit on it.