Resource Cost Reduction
From Diablo Wiki
Resource Cost Reduction (or RCR) refers to item properties, skill effects, or Paragon Points that lower the resource cost of an ability. The term can refer to anything that reduces the resource cost (some rune effects modify the base skill to this end), but it generally refers to an item bonus or Paragon Point that cuts the resource cost of all skills or a specific skill by a percentage.
The % based effect makes this bonus viable for all types of skills, since resource costs vary so much between skills and between classes. A flat reduction of 1 or 2 or 5 resource points wouldn't work, as some skills cost only a few resource points while others are 20 or 40 or more.
RCR Via Paragon Points
There are many items that grant resource cost reduction, typically from 5-10% via an item bonus.
RCR can also be obtained from Paragon Points spent in the Utility Tab, where the bonus is +.20% per paragon point. Thus 5 points = 1% Resource Cost Reduction and the maximum benefit from all 50 Paragon points in that field is 10% Resource Cost Reduction.