How does Pack Flow work on the A320? I am referring to an Airbus A320. I have heard of Pack Flow but I don't understand it.

If you put it on High, does that mean that all the parts of the air conditioning system work faster and harder?

I have also heard that if you put it on High, that means the demand for air supply is high, and vice versa, i.e. if it's on low then the supply for air is low, but what about NORM, or Economy flow?
Source: FCOM A320 familly

From the flight crew operating manual (FCOM) about the pack flow selector (4):


  Permits the selection of pack valve flow, according to the number of
  passengers and ambient conditions (smoke removal, hot or wet
  conditions).
   LO (80 %)  - NORM (100 %) - Hl (120 %).
  
  Manual selection is irrelevant in single pack operation, or with APU 
  bleed supply. ln
  these cases, Hl is automatically selected.
  
  lf LO is selected, the
  pack flow can be automatically selected up to 100 % when the cooling
  demand cannot be satisfied.


So to answer your question directly:


The normal flow (100%) is when the selector is on position NORM.
Position HI adds 20% to the air flow, and LO removes 20%.


In addition:


In LO position, the flow can be increased by the controller up to 100% in case the temperature cannot be obtained with only 80%.
In case of single pack operation, the flow is automatically set by the controller to 120%.