Aeration involves perforating the soil with small holes to allow air, water and nutrients to penetrate the grass's roots. This helps the roots grow deeply and produce a stronger, more vigorous lawn.
The main reason for aerating is to alleviate soil compaction. Compacted soils have too many solid particles in a certain volume or space, which prevents proper circulation of air, water and nutrients within the soil. Excess lawn thatch or heavy organic debris buried under the grass surface can also starve the roots from these essential elements.