What does the checkbox "Build target platform based on the target's installed plug-ins" do?

In Window -> Preferences -> Plug-in Development -> Target Platform, there is a checkbox "Build targe开发者_如何学Got platform based on the target's installed plug-ins". What is this asking?

I am using Eclipse 3.4.2

Hit F1 to open the Help and you'll find the following:

How PDE builds it target platform is dictated by the Build target platform based on target's installed plug-ins preference. When this preference is enabled, PDE will attempt to locate the target location's list of installed plug-ins inside a configuration file (platform.xml or bundles.info). If PDE finds this file, it will build the target platform based on the plug-ins inside the configuration file. If it doesn't find the file, PDE will just manually scan the target location directory for the list of plug-ins.

HTH Tom