All devices on the Web are identified 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 open it is to save you time, but the server where your website files are still has an IP address. Since there are a lot more websites and devices than there're IPs, all shared website hosting servers have a number of websites under the same IP, while using a dedicated server you'll get a dedicated IP too. Even in the first case though, you are able to acquire a dedicated IP for your sites and host them on a shared server. One benefit would be that you may enjoy far better search engine rankings as a dedicated IP often means a quicker loading site. Furthermore, you need such an IP in case you want to acquire an SSL certificate for your website and protect the information that your visitors submit on it.