#HarHarMahadev
The three eyes of #shiva are the representation or also origin of three vital forms sustaining life — sun, moon and fire. As stated in shiv panchakshari mantra itself
चंद्रार्क वैश्वानर लोचनाय
Of eyes being moon, sun and fire

The sun is represented by right eye while moon by left and third is agni.
Sun is the basic source of energy for earthly life. Moon is praised as king of vanaspatias or vegetable as it is through amrit dropped from rays of moon that these grow.

Fire is essential for consumption of food by humans( cooking in its materialistic form and for digestion in its jatharagni form) or gods ( the havis bearer form) or amcestors ( the kavya bearer form).
Thus the trinetras are symbolisation of sustainance of life.

This is why after mentioning many names in chamkam or rudra suktam , when yajur veda bhagwan came to pray for liberation from death he calls him tryambam ( having three eyes) instead of using words life mritunjay