An IP address is a unique number that distinguishes a site or a hosting server on the world-wide web, so if you have a dedicated IP, it will be employed just by your sites and won't be shared with others as it happens with shared Internet hosting accounts. Provided you have your own hosting server, you shall have a dedicated IP, but you may need additional ones for many different uses. If you have an online store, for instance, you will need an SSL certificate for it, to make sure that the payment info your clients submit will be encrypted and safe. The same is valid in case you have a login form of some kind and you would like the usernames and the passwords that visitors type in to be protected. The SSL certificate requires a dedicated IP address, which should be different from the one which you already have on the web server. You could also need an individual IP for an application such as a VoIP server, or if you would like a slightly better performance for a particular site, which will influence its position in search engine results.