editing version 1
No till is about not tilling or disturbing the land when gardening / farming. This insight is based on the observation that plants grow in nature without anyone tilling it, and they grow lush and vigorous while producing abundant fruits and seeds. Tilling exposes the soil to the elements - sunshine, rain, wind and causes erosion, death of delicate soil life. The unwanted plants that we label as "weeds" simply come back stronger since the soil is loose and those plants play a role in holding the soil together. Tilling, although seems to produce good crops in the short run, is degrading the overall health of the soil - in all it's interconnected diversity. One could say the practice of tilling the soil arose when human being tried to get large, fast harvests while treating his soil like a unit in a factory, without regard to life and richness of nature. No till lies at the heart of /natural_farming and /permaculture.