Aeration allows air, water and nutrients to penetrate the grass roots. This helps the roots grow deeply and produce a stronger, more healthier 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.
Your lawn is probably a good candidate for aeration if it:
Was established as part of a newly constructed home. Often, the topsoil of newly constructed lawns is stripped or buried, and the grass established on subsoil has been compacted by construction traffic.
Was established by sod, and soil layering exists. Soil layering means that soil of finer texture, which comes with imported sod, is layered over the existing coarser soil. This layering disrupts drainage, as water is held in the finer-textured soil. This leads to compacted conditions and poor root development. Aerating breaks up the layering, allowing water to flow through the soil more easily and reach the roots.