arranging the values in particular order
(i)Lower to higher
(ii)Higher to Lower

DRILL DOWN(+)
 default hierarchy is drill down
 Result is higher to lower level
DRILL UP(-)
 lower to higher
Drill across: There is no order.

In tableau we cann't use one dimension from one hierachy and another dimension from another heirachy. To over come that we will make duplicate and we can use hierachy.