Guṇa (Sanskrit: गुण) means 'string' or 'a single thread or strand of a cord or twine'. In more abstract uses, it may mean 'a subdivision, species, kind, quality', or an operational principle or tendency.
In Samkhya philosophy, there are three major guṇas that serve as the fundamental operating principles or 'tendencies' of prakṛti (universal nature) which are called: sattva guṇa, rajas guṇa, and tamas guṇa. The three primary gunas are generally accepted to be associated with creation (sattva), preservation (rajas), and destruction (tamas) (see also Aum and Trimurti). The entire creation and its process of evolution is carried out by these three major gunas.
Read more about Guṇa: In Classical Literature, Bhagavad Gita, In Samkhya Philosophy, In Nyaya Philosophy, In Grammar