An IP address is a unique number which distinguishes a website or a hosting server on the Internet, so in the event that you have a dedicated IP, it will be employed only by your Internet sites and will not be shared with other people as it happens with shared web hosting accounts. If you have your own server, you shall have a dedicated IP, but you may require additional ones for different uses. If you have an Internet store, for instance, you'll need an SSL certificate for it, in order to ensure that the payment information that your customers submit will be encrypted and protected. The same is valid in case you have a login form of some type and you want the usernames and the passwords that visitors enter to be protected. The SSL certificate requires a dedicated IP, which needs to be different from the one that you already have on the web server. You might also need an independent IP for an app such as a VoIP server, or if you want a slightly better efficiency for a particular site, which shall affect its position in search engine results.