An IP address is a unique number which identifies a site or a server on the world-wide web, so if you have a dedicated IP, it shall be used only by your Internet sites and will not be shared with other individuals as it happens with shared web hosting accounts. Provided you have your own web server, you will have a dedicated IP, but you may require additional ones for various purposes. In case you have a web-based store, for example, you shall need an SSL certificate for it, in order to make sure that the payment information your clients submit will be encrypted and secure. The same is valid in case you have a login form of some kind 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 could also need an individual IP for an app such as a VoIP server, or if you desire a slightly better functionality for a certain website, which may influence its position in search engine results.