In simple terms, aeration means making holes in the ground to allow air, water, and nutrients to reach the grassroots. It might seem unnecessary, but some soil conditions can make it hard for grass to get the nourishment it needs. Soil that has become too compact will starve the roots of these important elements. The build-up of thatch and debris will contribute to nourishment issues as well. Aerating reduces soil compaction and creates a path through the debris, making way for air, water, and nutrients.

Aeration contributes to the health of your lawn and will reduce the amount of work required to maintain it. 

Some benefits include: improved air circulation; increased water flow to the soil; reduced water puddling and runoff; reduced soil compaction; stronger roots; improved thatch breakdown; better heat tolerance; fewer pest problems; easier to maintain.