All devices on the World Wide Web are recognized by a special number called an IP address, for instance 188.8.131.52. If you have a site, the domain that you enter to access it is for your convenience, yet the server where the website files are still has an IP. Since there are a lot more sites and devices than there are IP addresses, all shared web hosting servers have a number of sites under the same IP, whereas using a dedicated server you'll have a dedicated IP too. Even in the first case though, you will be able to obtain a dedicated IP for your websites and host them on a shared server. One advantage would be that you'll have better search engine positions because a dedicated IP often means a quicker loading site. Last but not least, you need such an IP if you would like to acquire an SSL certificate for your website and protect the info that visitors submit on it.