Expression value

[Samuel Blin]

Hi all,
In the war plugin source code I found this:

   /**
    * The Jar archiver.
    *
    * @parameter expression="${
component.org.codehaus.plexus.archiver.Archiver#war}"
    * @required
    */
   private WarArchiver warArchiver;

I understand the meaning of "@parameter" and "expression" but not the value
of the expression parameter. What does it mean?
Where could I find documentation to explain all the supported syntax?

Thanks,

Samuel