[ZPT] ++ as "location"

[Rakotomandimby Mihamina]

Hi,
In many templates I run into, I notice this, for example in this one:
https://svn.nuxeo.org/trac/pub/file/CPSMailAccess/trunk/www/mailZemanticSearchView.zpt

What's the use of the "++"?
It's OK for me to learn but I did not find simple templates examples :-)
This one is a very complicated one for me...

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