Aerating is important because it ensures the soil is getting plenty of air which helps to stimulate root growth. Aeration is recomended for hard compacted lawns, clay soils, lawns with very little top soil. Aerating involves the removal of small soil plugs from your lawn. The core aerating process extracts a 3/4 inch diameter hole out of the ground. Aeration holes typically run 3 inches deep and 3 to 5 inches apart and is a recommended lawn care practice on compacted heavily used turf and to control thatch buildup.