An IP address is a unique number which distinguishes a site or a server on the world-wide web, so in the event that you have a dedicated IP, it will be employed solely by your sites and shall not be shared with other people as it happens with shared hosting accounts. In case you have your own web server, you shall have a dedicated IP, but you may need extra ones for different purposes. If you have an electronic store, for instance, you shall need an SSL certificate for it, in order to ensure that the payment info your customers submit will be encrypted and protected. The same is valid in the event that you have a login form of some kind and you would like the usernames and the passwords that visitors enter to be protected. The SSL certificate requires a dedicated IP address, which ought to be different from the one which you already have on the web server. You could also need an independent IP for an application such as a VoIP server, or if you need a slightly better performance for a given site, which may influence its position in search engine results.