Measures represent values that are counted, summarized, or aggregated, such as costs. Measures include "simple" measures (amounts paid, days worked, etc.) as well as computed measures or ratios, such as cost per employee per month.
A measure is the combination of a numeric input column with a roll-up rule or statistic.
Aggregating measures allow you to calculate the Sum, Minimum, Maximum, Count, Mean, or Distinct Count for the field data you are aggregating.