Where to look for 'maincatalog' ([email protected])?

Question

MODX

There is a code:

<div class="catalog__content">
        <!-- catalog-->
        [[[email protected]?
        &conditional-Tpls=`{"19":"sub.catalog.row2"}`
        &tplCondition=`id`
        &tplOperator=`==`
        &depth=`0`
        &select=`id,pagetitle,class`
        ]]
    </div>

It outputs all categories and subcategories of the menu. It is necessary to display their subcategories on the pages of categories. I can't figure out where to look for "maincatalog".
For the first time I meet such a construction ([email protected]). I suspect that the maincatalog says what resources to display.