An IP address is a unique number that distinguishes an Internet site or a web server on the Internet, so in the event that you have a dedicated IP, it'll be used only by your Internet sites and won't be shared with other people as it happens with shared website hosting accounts. Provided you have your own hosting server, you will have a dedicated IP, but you may require additional ones for different uses. Provided you have an Internet store, for example, you shall need an SSL certificate for it, in order to make certain that the payment info that your clients submit will be encrypted and protected. The same is valid in the event that you have a login form of some type and you would like the usernames and the passwords which 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 web server. You could also need an independent IP for an application such as a VoIP server, or if you desire a slightly better overall performance for a certain Internet site, which will influence its position in search engine results.