All devices on the World Wide Web are recognized by a specific number called an IP address, for instance 220.127.116.11. When you have a website, the domain name that you type to access it is for your convenience, but the server where the website files are still has an IP address. Since there're many more sites and devices than there are IP addresses, all the shared hosting servers have a number of websites under an identical IP, while using a dedicated server you'll get 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 advantage would be that you will have far better search engine rankings as a dedicated IP usually means a quicker loading site. In addition, you need such an IP if you want to purchase an SSL certificate for your website and secure the info that your visitors submit on it.