All devices on the Web are recognized by a unique number called an IP address, for instance 220.127.116.11. When you have a website, the domain that you enter in order to load it is to save you time, however the server where the site files are still has an IP. Considering that there are far more sites and devices than there're IP addresses, all the shared web hosting servers have a number of sites under the very same IP, while when you use a dedicated server you'll be given a dedicated IP as well. Even in the first case though, you are able to obtain a dedicated IP for your websites and host them on a shared server. An advantage would be that you'll get superior search engine positions as a dedicated IP usually means a faster loading website. What's more, you need such an IP when you intend to purchase an SSL certificate for your website and protect the information that your visitors submit on it.