Karma means prescribed duties. Prescribed duties. Janma-karma. Guṇa-karma. Cātur-varṇyaṁ mayā sṛṣṭaṁ guṇa-karma-vibhāgaśaḥ (BG 4.13). Guṇa-karma. Cātur-varṇyam. According to Vedic civilization, there are four divisions of karma. Because there are three qualities of the material nature: sattva-guṇa, rajo-guṇa, tamo-guṇa. So when we come to certain type of activities or accept certain type of body, Kṛṣṇa is giving us opportunity. I wanted certain type of body; Kṛṣṇa is giving. Kṛṣṇa is giving through the agency of material nature. Kāraṇaṁ guṇa-saṅgo 'sya sad-asad-janma-yoniṣu (BG 13.22).
Why the living entities having different types of body? Sat asat. Some types of body are nice. Suppose you become demigod, Indra, Candra. That's very nice. But if you become dog or worm in the stool, that is not very nice. But we have to. Why? Kāraṇam . . . the reason is, guṇa-saṅgaḥ asya. As we associate with the guṇas . . . there are three guṇas, qualities of the material nature: sattva-guṇa, rajo-guṇa, tamo-guṇa.
So if we associate with sattva-guṇa, ūrdhvaṁ gacchanti sattva-sthā (BG 14.18), then those who are associating with sattva-guṇa . . . this is very easy to understand. If you become a nice, educated person, good character, you'll be always welcome anywhere, good position. And if you are a thief, rascal, without any education, then your position will be different. So kāraṇaṁ guṇa-saṅgaḥ asya. So if we associate with goodness of the material nature, then we are promoted to the higher planetary system where we get better comforts of life, long duration of life, so many facilities.
Similarly ūrdhvaṁ gacchanti sattva-sthā madhye tiṣṭhanti rājasāḥ (BG 14.18). Those who are associating with the qualities of passion, they remain within this middle planetary system, bhūr bhuvaḥ svaḥ. And then . . . jaghanya-guṇa-vṛtti-sthā adho gacchanti tāmasāḥ. And if we associate with tāmasika qualities, then we degraded to lower species of life, lower planetary system, dark planetary system. There are many planets, they are dark. As we have got a part of this planet also, six months dark, six months light . . . there are so many different varieties of planets. This is the . . . we are wandering from different planetary systems . . . different . . . this way. Kāraṇaṁ guṇa-saṅgaḥ asya.