An IP address is a unique number which separates a site or a web server on the Internet, so if you have a dedicated IP, it shall be employed only by your sites and shall not be shared with others as it happens with shared Internet hosting accounts. In case you have your own web server, you will have a dedicated IP, but you may need additional ones for many different uses. If you have a web-based store, for example, you shall need an SSL certificate for it, so as to ensure that the payment information which your clients submit will be encrypted and secure. The same is valid if you have a login form of some type and you want the usernames and the passwords that visitors enter to be protected. The SSL certificate requires a dedicated IP address, which has to be different from the one which you already have on the web server. You could also need an individual IP for an app such as a VoIP server, or if you would like a slightly better functionality for a particular site, which shall affect its position in search engine results.