To filter a report, enter values in the filter row as shown in this screenshot:
To group a report, drag a column header and drop it onto the section titled 'Drag a column header here to group by that column'. The end result will look like this:
Note: you can group by more than one column. Simply drag as many columns to the grouping section as you'd like.
Note: to remove grouping simply drag the column header back to the report.
To drilldown into a report click the '+' sign as shown here: