The document discusses the seven distinct agro-climatic zones of Tamil Nadu: 1) North Eastern zone, 2) North Western zone, 3) Western zone, 4) Cauvery Delta zone, 5) Southern zone, 6) High Rainfall zone, 7) Hilly zone. Each zone is defined based on its geographical location, climate patterns like rainfall and temperature, soil types, and included districts. The zones vary in their climatic conditions like average rainfall, temperature ranges, and types of crops suitable for each region.