The Faceted Project Framework allows creation of modular projects in Eclipse so that the user can easily add and remove functionality. All WTP projects leverage this framework, but it can also be used independent of WTP.
The JDT Enablement component extends the
Faceted Project Framework to integrate with Java Development Tools. The component includes the Java facet, modeling of the JVM-based runtimes and tools for simplifying Java library management for facet authors.
Note: you only need this zip file(s) if you want to use only this function. If you download the WTP (or WST) zip file, it is already included there.