All devices on the Internet are recognized by a special number called an IP address, such as 123.123.123.123. When you have a website, the domain that you enter to be able to load it is to save you time, yet the server where your site files are still has an IP address. Considering that there're many more websites and devices than there are IP addresses, all the shared website hosting servers have a number of sites under the very same IP, whereas when you use a dedicated server you will have a dedicated IP as well. Even in the first case though, you'll be able to acquire a dedicated IP for your websites and host them on a shared server. An advantage would be that you will have superior search engine positions because a dedicated IP generally means a faster loading website. Last but not least, you need such an IP if you want to obtain an SSL certificate for your website and secure the info that your visitors submit on it.