Icons and Icon Decorations in Eclipse

I saw an unfamiliar icon decoration today and wanted to know what it meant. I found this answer on StackOverflow and wanted to link to it in case anyone else wanted to know about Eclipse icons and Eclipse icon decorations in the Package Explorer.

Thanks to Lord Torgamus for the excellent answer on StackOverflow!

His answer (as found on StackOverflow)

This is a fairly comprehensive list from the Eclipse documentation. If anyone knows of another list — maybe with more details, or just the most common icons — feel free to add it. 

Helios: http://help.eclipse.org/helios/index.jsp?topic=/org.eclipse.jdt.doc.user/reference/ref-icons.htm 

Galileo: http://help.eclipse.org/galileo/topic/org.eclipse.jdt.doc.user/reference/ref-icons.htm?resultof=%22icon%22 

There are also some CDT icons at the bottom of this help page. 

If you're a Subversion user, the icons you're looking for may actually belong to Subclipse; see this excellent answer for more on those.