Aerating is done to loosen/soften ground to allow grass roots to penetrate deeper and for soil to accept new grass seed easily. An aerating machine has a spindle that spins has it propels itself and poke ¾-1” holes into the ground about 4-5” inches deep. Loosening the soil allows air to circulate, nutrients and water to reach deeper. The root system will go deeper following water and nutrients. Deep roots is not only beneficial but a money saver. If roots remain close to surface, it will require more water. The sun dries out surface dirt very quickly and easily, an aerated turf allows water to push deeper easier where it remains cool, and where water has pushed nutrients, the grass roots will follow which then become thicker and more resilient to pest and diseases.