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