An IP address is a unique number that identifies an Internet site or a hosting server on the Internet, so if you have a dedicated IP, it shall be employed just by your sites and shall not be shared with other people as it happens with shared website hosting accounts. If you have your own server, you'll have a dedicated IP, but you may require additional ones for a variety of uses. Provided you have an Internet store, for instance, you shall need an SSL certificate for it, so as to make sure that the payment info which your clients submit will be encrypted and safe. The same is valid in case you have a login form of some type and you would like the usernames and the passwords which visitors input 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 hosting server. You may also need an independent IP for an application such as a VoIP server, or if you want a slightly better overall performance for a certain website, which shall affect its position in search engine results.