In the Eclipse Package Explorer view, objects can have a decoration consisting of an orange rectangle (or cylinder), for example:
I can not find it in the icon link for Eclipse Indigo.
What does it mean?
This means that the file is under version control. (i.e. cvs, svn, git or something else)
You can find the meaning here: http://www.rorycullen.com/blog/2009/07/guide-to-subclipse-decorator-icons/
maybe not your version control system, but it's pretty standard in eclipse.
