All devices on the World Wide Web are recognized by a specific number called an IP address, such as 123.123.123.123. In case you have a site, the domain name that you type to load it is for your convenience, however the server where the site files are still has an IP address. Since there are far more sites and devices than there are IP addresses, all the shared web hosting servers have a number of websites under an identical IP, whereas when you use 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 sites and host them on a shared server. One advantage would be that you'll enjoy superior search engine rankings since a dedicated IP generally means a faster loading site. What's more, you need such an IP when you intend to obtain an SSL certificate for your site and shield the information that your visitors submit on it.