Here is an excerpt from Chapter 14 of the first draft of the Bhagavad-Gita presentation I am working on.
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Krishna: Prakṛti, “Nature” is the first thing produced from the singularity. It has three qualities: sattva, rajas, and tamas. My strong friend, these three are the ropes that bind the limitless living being to a body.
Arjuna: Can you explain more about each quality?
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Krishna: Sattva is clear and undistorted and therefore allows the illumination of consciousness to shine brightly. Its rope, though, is the desire for happiness and comprehension.
Rajas is distorted by passion. Its ropes around the living being are ever-rising thirsts and endeavors.
Tamas is the strongest of all. It darkens with ignorance and thus bewilders every soul. It has many ropes, like foolishness, laziness and stagnation.
In summary: Sattva creates happiness. Rajas creates efforts. Tamas eclipses knowledge and creates foolishness.
A Simple Gita 