All devices on the Web are recognized by a unique number called an IP address, for instance 123.123.123.123. When you have a site, the domain that you enter in order to access it is to save you time, yet the server where the site files are still has an IP address. Considering that there are a lot more websites and devices than there're IPs, all of the shared hosting servers have a number of websites under an identical IP, whereas with a dedicated server you'll get a dedicated IP too. Even in the first case though, you're able to acquire a dedicated IP for your websites and host them on a shared server. One benefit would be that you'll get superior search engine positions as a dedicated IP usually means a faster loading website. Last but not least, you need such an IP if you plan to get an SSL certificate for your site and secure the info that your visitors submit on it.