Can someone explain what this is in the ui component xml

Question

Can someone explain what ${$.$data} is doing in sales_order_grid.xml

 <columns name="sales_order_columns">
    <argument name="data" xsi:type="array">
        <item name="config" xsi:type="array">
            <item name="childDefaults" xsi:type="array">
                <item name="fieldAction" xsi:type="array">
                    <item name="provider" xsi:type="string">sales_order_grid.sales_order_grid.sales_order_columns.actions</item>
                    <item name="target" xsi:type="string">applyAction</item>
                    <item name="params" xsi:type="array">
                        <item name="0" xsi:type="string">view</item>
                        <item name="1" xsi:type="string">${ $.$data.rowIndex }</item>
                    </item>
                </item>
            </item>
        </item>

Answer 1

This layout will dynamic load data from row from js render. When sales_order_grid render columns layout will get data from js and render it to browser. $.$data.rowIndex represent to sales_order_grid get property data and get rowIndex