An IP address is a unique number that separates a website or a hosting server on the Internet, so if you have a dedicated IP, it'll be used exclusively by your Internet sites and shall not be shared with other individuals as it happens with shared hosting accounts. In case you have your own hosting server, you'll have a dedicated IP, but you may require extra ones for different uses. If you have a web-based store, for instance, you shall need an SSL certificate for it, to ensure that the payment info which your customers submit shall be encrypted and protected. The same is valid in case you have a login form of some type and you wish the usernames and the passwords which visitors input to be secured. The SSL certificate requires a dedicated IP address, which needs to be different from the one which you already have on the server. You might also need an independent IP for an application such as a VoIP server, or if you would like a slightly better efficiency for a certain Internet site, which will affect its position in search engine results.