See this document for a description of the rationale.

Directory or file nameDescription
LICENSE.txtLicense file. This project is released under ASL.
src/javaJava source code
etcProject configuration Files - should be moved to src/conf
src/testUnit test source code
src/test/etcUnit test configuration files - should be moved to src/test/conf
src/test/confUnit test configuration files - only goals-grabber uses it for now
src/conf/eclipseEclipse plugin artifact description files - site.xml, feature.xml or plugin.xml
xdocs/XML Documentation files
project.propertiesSpecific project properties

Default Maven layout is used.

Directory or file nameDescription
plugin.xmlEclipse plugin descriptor
feature.xmlEclipse feature descriptor
site.xmlEclipse update site descriptor
libEclipse plugin libraries
target/eclipse/distEclipse binary artifact - plugin, feature or site
target/eclipse/dist/pluginsEclipse plugins - if current project is of type 'feature' or 'site'
target/eclipse/dist/featuresEclipse features - if current project is of type 'site'