An IP address is a unique number that identifies an Internet site or a hosting server on the world-wide web, so in the event that you have a dedicated IP, it'll be used just by your Internet sites and won't be shared with others as it happens with shared hosting accounts. In case you have your own server, you will have a dedicated IP, but you may require extra ones for many different purposes. If you have an Internet store, for example, you'll need an SSL certificate for it, to make sure that the payment information which your customers submit will be encrypted and secure. The same is valid in case you have a login form of some kind and you want the usernames and the passwords that visitors type in to be secured. The SSL certificate requires a dedicated IP address, which ought 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 need a slightly better performance for a given site, which shall influence its position in search engine results.