All devices on the Internet are identified by a special number called an IP address, such as 123.123.123.123. If you have a website, the domain name that you enter in order to open it is for your convenience, however the server where the site files are still has an IP address. Considering that there are many more sites and devices than there are IP addresses, all the shared web hosting servers have a number of sites under an identical IP, while with a dedicated server you'll have a dedicated IP too. Even in the first case though, you're able to get a dedicated IP for your websites and host them on a shared server. One benefit would be that you may get far better search engine rankings as a dedicated IP generally means a faster loading site. Last but not least, you need such an IP when you plan to purchase an SSL certificate for your site and protect the info that your visitors submit on it.