All devices on the World Wide Web are recognized by a special number called an IP address, such as 220.127.116.11. If you have a website, the domain name that you type to access it is for your convenience, however the server where your site files are still has an IP address. Since there are many more sites and devices than there're IP addresses, all the shared web hosting servers have a number of websites under the same IP, whereas when you use a dedicated server you'll have a dedicated IP as well. Even in the first case though, you can get a dedicated IP for your websites and host them on a shared server. One advantage would be that you'll enjoy improved search engine rankings since a dedicated IP usually means a faster loading website. Furthermore, you need such an IP if you would like to acquire an SSL certificate for your site and secure the data that your visitors submit on it.