A shared IP address is one address or "location" that is used for multiple sites. Typically lower priced hosting plans will be put on a server with many other accounts all sharing the same IP address. The IP address that they all share is a number assigned to that particular server. A shared IP can host all sites on a webserver. Because the IP address of a website is used for various sites on the server the actions of one site owner can affect everyone on the server. For example, if an IP address is blacklisted for spamming this will blacklist mail for ALL websites using the shared IP address. We work hard to prevent and to resolve these issues immediately and take corrective action against anyone who abuses the system. You will not be able to install an SSL certificate if your site is on a shared IP.
A dedicated IP address for your account specifically (that no other website uses) may be ordered at this address... http://www.ultrawebhosting.com/upgrades