CALCULATE : The most powerful function, used to modify the filter context of a calculation.
If you're looking for the "power" in PowerPivot, these common DAX functions highlighted by expert resources like Microsoft Support and Analytics Vidhya are essential: Practical PowerPivot & DAX Formulas for Excel
RANKX : Automatically ranks items (like products or sales reps) based on a specific value. Practical PowerPivot & DAX Formulas for Excel 2010 CALCULATE : The most powerful function, used to
: Practical examples show how to compare current performance against the past and handle tricky calculations like running totals or non-numeric values. CALCULATE : The most powerful function