Velocity Reserved Words

I was googleing for these keywords "velocity reserved words". I need to know what they are!

I did't find nothing useful and also at Velocity Reference I haven't found what I need.

Just a few day days ago I was editing a Content Model, for an Attach Attribute, and I wanted to show the size. The code was something like $content.Attach.resource.instance.fileLenght (yeah there's a typo error in getter!) and not working.

So what's wrong with "resource" and "instance" in velocity? :) Solution was to add a custom getter to the object with a different name.

Mhh I'm still not convinced about Velocity Reserved Words.