An IP address is a unique number which identifies an Internet site or a hosting server on the Internet, so if you have a dedicated IP, it will be used exclusively by your websites and shall not be shared with other individuals as it happens with shared hosting accounts. If you have your own hosting server, you will have a dedicated IP, but you may require extra ones for various purposes. In case you have an online store, for instance, you will need an SSL certificate for it, to make sure that the payment information your customers submit will be encrypted and safe. The same is valid in case you have a login form of some type and you want the usernames and the passwords that visitors enter to be secured. The SSL certificate requires a dedicated IP, which has to be different from the one which you already have on the hosting server. You might also need an individual IP for an app such as a VoIP server, or if you need a slightly better overall performance for a particular Internet site, which may affect its position in search engine results.