All devices on the Web are recognized by a special number called an IP address, for example 123.123.123.123. In case you have a site, the domain name that you enter to load it is to save you time, yet the server where your website files are still has an IP address. Considering that there're many more websites and devices than there're IP addresses, all shared web hosting servers have a number of sites under an identical IP, whereas with a dedicated server you'll get a dedicated IP too. Even in the first case though, you're able to get a dedicated IP for your sites and host them on a shared server. An advantage would be that you will get far better search engine rankings as a dedicated IP often means a quicker loading website. What's more, you need such an IP if you intend to buy an SSL certificate for your website and protect the data that visitors submit on it.