Core aeration is the process of perforating the soil, allowing air, water and nutrients to penetrate the grass roots. This process helps the roots grow deeper thus being stronger and producing a better quality lawn. The main reason for aeration is to create a less compacted soil allowing for proper circulation. It also helps with excess thatch; however, thatch is good for the lawn as long as it is no more than 1/2 inch. This is why aerating in some cases can be more beneficial than raking the lawn. Raking the lawn with a power rake or rakes attached to the mower can remove the important "healthy" thatch that is needed for the lawn to stay healthy and strong.