Following up on this post on the translation of Guru Nanak's poem in the color of hope (Click here for translation), following is info from Wikipedia on the six orthodox systems:
Several Indian intellectual traditions were codified during the medieval period into a standard list of six orthodox systems or ṣaḍdarśanas, all of which cite Vedic authority as their source.Nyaya, Vaisheshika, Samkhya, Yoga, Mimāṃsā and Vedanta are classified as āstika schools:
Nyāyá, the school of logic
Vaiśeṣika, the atomist school
Sāṃkhya, the enumeration school
Yoga, the school of Patañjali (which assumes the metaphysics of Sāṃkhya)
Mimāṃsā, the tradition of Vedic exegesis
Vedanta or Uttara Mimāṃsā, the Upaniṣadic tradition.
These are often coupled into three groups for both historical and conceptual reasons: Nyāyá-Vaiśeṣika, Sāṃkhya-Yoga, and Mimāṃsā-Vedanta.