An IP address is a unique number that identifies a website or a server on the world-wide web, so if you have a dedicated IP, it shall be used only by your sites and shall not be shared with other people as it happens with shared website hosting accounts. If you have your own hosting server, you will have a dedicated IP, but you may need additional ones for a variety of purposes. Provided you have a web-based store, for instance, you shall need an SSL certificate for it, to make certain that the payment information which your clients submit shall be encrypted and protected. The same is valid if you have a login form of some sort and you wish the usernames and the passwords which visitors enter to be secured. The SSL certificate requires a dedicated IP address, which needs to be different from the one that you already have on the server. You may also need an individual IP for an application such as a VoIP server, or if you desire a slightly better functionality for a certain Internet site, which shall influence its position in search engine results.