All devices on the Internet are recognized by a unique number called an IP address, such as 220.127.116.11. In case you have a website, the domain name that you enter to access it is for your convenience, however the server where your website files are still has an IP. As there are a lot more websites and devices than there're IP addresses, all shared hosting servers have a number of sites under the same IP, while using a dedicated server you'll get a dedicated IP as well. Even in the first case though, you're able to acquire a dedicated IP for your sites and host them on a shared server. An advantage would be that you'll get superior search engine positions since a dedicated IP often means a quicker loading site. What's more, you need such an IP in case you would like to purchase an SSL certificate for your website and secure the information that your visitors submit on it.