All devices on the World Wide Web are recognized by a unique number called an IP address, for example 123.123.123.123. If you have a website, the domain that you enter to be able to load it is for your convenience, but the server where your site files are still has an IP address. Considering that there are a lot more sites and devices than there are IP addresses, all the shared web hosting servers have a number of sites under the very same IP, while using a dedicated server you will have a dedicated IP as well. Even in the first case though, you can get a dedicated IP for your websites and host them on a shared server. One advantage would be that you will get better search engine positions as a dedicated IP generally means a faster loading site. What's more, you need such an IP when you would like to buy an SSL certificate for your site and protect the data that your visitors submit on it.