(1) Quality, a natural tendency. Some people have many Gun or qualities for which they become very famous or popular. They are the good habits which people like and praise him for that, such as speaking truth, making friends, always smiling; and there maybe many.

Its opposite is Avagun - means he characteristics which are not good, like stealing, lying, living in a dirty way etc etc.

(2) There are three Gun, called also Tri-Gun - 
1. Saatwik, or Sato Gun (Goodness) is the tendency to think and perform virtuous deeds, like Sthiti and maintenance, patience, regularity, affection, sympathy, care for food, clothing, residence etc essential needs of Brahmchaaree.
2. Raajas, or Rajo Gun (Passion) denotes the passion for acquiring worldly pleasures. Utpatti or Creativity. Capability of thinking and generating teaching aids and other needs of the Brahmchaaree - books, notes, charts, illustrations etc. (Brahmaa Jee created this world with his Rajo Gun)
3. Taamasik, or Tamo Gun (Inertia) denotes laziness and ignorance. Dissolution. Extreme peak of excellence in knowledge, striving for deleting or wiping off the ignorance and bad habits of Brahmchaaree.

Since they are the attributes, these can be attached to many things, for example, Tri-Gunee Prakriti, Tri-Gunee Karm, Tri-Gunee creation, etc. All men are said to have all three natures, but in different proportions. The ideal nature is to shed Raajas and Taamas nature and adopt for pure Saatwik nature.

Gun Tattwa - Sattwa, Rajas, and Tamas, transform into good and evil fruits causing happiness and misery. Each one of the Gun take two more Gun and thus in all there are nine Gun. Sattva = Virtue and goodness; Rajas = motion and passion; and Tamas = Darkness and sloth. Gun, modes, attributes, or qualities do not manifest themselves as long as they are in equilibrium, which is compared to the fragrance in the bud, meaning that the fragrance remains unrevealed.

Gun Vibhaag and Karm Vibhaag
All the ten Indriyaan (5 Gyaanendriya and 5 Karmendriya), their five pleasures (seeing, smelling, hearing, tasting and feeling), three Gun (Sat, Raj, and Tam), Maayaa's five Mahaabhoot (fire, air, earth, water and sky), Man (mind), Buddhi (intelligence), Ahankaar all Tattwa (elements) jointly are called "Gun Vibhaag" and their actions are called "Karm Vibhaag". Vibhaag means division or sections. When somebody knows Aatmaa (soul), which is separate from "Gun Vibhaag" and "Karm Vibhaag", he is said to know about Tattwa (element).