An IP address is a unique number that identifies a website or a hosting server on the Internet, so in the event that you have a dedicated IP, it will be used just by your websites and will not be shared with others as it happens with shared hosting accounts. Provided you have your own web server, you will have a dedicated IP, but you may need additional ones for various uses. 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 shall be encrypted and safe. The same is valid if you have a login form of some kind and you would like the usernames and the passwords which visitors input to be secured. The SSL certificate requires a dedicated IP address, which ought to be different from the one that you already have on the server. You may also need an individual IP for an application such as a VoIP server, or if you desire a slightly better performance for a certain website, which shall affect its position in search engine results.