What is mining intensity? Both Bitcoin and Litecoin have an intensity setting when mining.  What does this mean?
Yes, this is related to GPU mining. From cgminer's README:


  INTENSITY INFORMATION:
  
  Intensity correlates with the size of work being submitted at any one
  time to a GPU. The higher the number the larger the size of work.
  Generally speaking finding an optimal value rather than the highest
  value is the correct approach as hash rate rises up to a point with
  higher intensities but above that, the device may be very slow to
  return responses, or produce errors.


I would just leave it set to 'dynamic,' or --intensity d . That will adjust it automatically depending on how long it takes to complete work.
(nitty-gritty details)