An IP address is a unique number which separates a site or a web server on the world-wide web, so if you have a dedicated IP, it'll be employed solely by your sites and will not be shared with others as it happens with shared web hosting accounts. In case you have your own hosting server, you shall have a dedicated IP, but you may need additional ones for different uses. Provided you have an online store, for instance, you will need an SSL certificate for it, in order to make certain that the payment information that your customers 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 type in to be protected. The SSL certificate requires a dedicated IP, which ought to be different from the one that you already have on the hosting server. You may also need a separate IP for an application such as a VoIP server, or if you desire a slightly better functionality for a particular site, which shall affect its position in search engine results.