An IP address is a unique number which separates a website or a server on the Internet, so if you have a dedicated IP, it'll be used just by your sites and won't be shared with other individuals as it happens with shared website hosting accounts. Provided you have your own hosting server, you'll have a dedicated IP, but you may require extra ones for many different uses. Provided you have an online store, for instance, you will need an SSL certificate for it, to make certain that the payment info which your clients submit will be encrypted and secure. The same is valid in the event that you have a login form of some sort and you would like the usernames and the passwords which visitors input to be protected. The SSL certificate requires a dedicated IP, which should be different from the one which you already have on the hosting server. You might also need an individual IP for an application such as a VoIP server, or if you want a slightly better functionality for a given website, which may influence its position in search engine results.