Material nature, or prakriti, is the Gita's word for the world of matter, body, senses and even the mind. It includes the qualities of nature called gunas: sattva (clarity), rajas (passion) and tamas (inertia). Understanding this can feel abstract, yet it has a practical use. It helps us see that many of our moods, urges and habits are movements of nature, not a verdict on who we are.
The Gita describes nature in some detail. Gita 7.4 lists eight components, including mind, intellect and ego, so even the inner instruments of thought belong to nature and are not the true Self. Gita 13.20 says that changes and the three qualities arise from nature, not from the self, and Gita 14.5 says goodness, passion and ignorance bind the soul to the body though the soul itself is untouched. Gita 3.27 says the ego mistakenly claims what nature performs.
This view comes with practical lessons. Gita 2.62 shows how constant thinking about objects creates attachment, craving and finally anger, and Gita 2.63 shows anger clouding judgment, so notice what your mind dwells on and pause before acting. Gita 3.37 calls desire and anger the chief enemy of wellbeing. Gita 17.3 says that faith shapes a person, so choose carefully what you trust. Observe which quality is shaping your mood and cultivate clarity and balance.