Gun has two meanings:-

(1) One meaning of Gun is intrinsic characteristic of Prakriti (nature), primordial nature. There are three Gun - 
(i) Sat or Sattwa or Saatwik, or Sato Gun - The Saatwik aspect refers to Divine aspect in man in contrast to the animal and human aspects in him. This Gun is characterized by purity, luminosity, lightness, harmony and production of pleasure. It is the purest aspect of all the three Gun.
(ii) Raj or Rajas or Raajas, or Rajo Gun - One of the three Gun that compose the Universe and all in it. It refers to human aspect in man in contrast to animal and Divine aspects in him. This Gun's qualities are vibration, activity and motion.
(iii) Tam, or Taamas, or Tamo Gun - One of the attributes of primordial nature - Prakriti. In this Gun energy tends to move downward. Its qualities are stability, stagnation, dullness, inertia, darkness.