All devices on the Web are identified by a specific number called an IP address, such as 123.123.123.123. When you have a website, the domain name that you type to access it is to save you time, yet the server where your website files are still has an IP. Since there are many more sites and devices than there're IP addresses, all of the shared web hosting servers have a number of sites under the same IP, whereas when you use a dedicated server you'll have a dedicated IP too. Even in the first case though, you are able to obtain a dedicated IP for your sites and host them on a shared server. An advantage would be that you will get better search engine rankings since a dedicated IP often means a quicker loading website. What is more, you need such an IP if you intend to acquire an SSL certificate for your site and protect the data that visitors submit on it.