"Callisto is a coordinated release of 10 projects for Eclipse that greatly simplify the process of getting Eclipse up and going so you can do what you want to do. Callisto isn't a different, customized version of Eclipse V3.2, nor is it a replacement of the projects included when you go to the Eclipse Callisto Discovery Site. Using the Callisto Discovery Site, it's easy to get all the projects you need for Web or Java 2 Platform, Enterprise Edition (J2EE) development without having to search for each plug-in and install it separately because the plug-ins are sorted by the type of activity they enable.
"Because it makes getting Eclipse tailored to your needs a simple task, the Callisto Discovery Site is a welcome addition in Eclipse V3.2..."