Lawn aeration is the secret weapon in making your lawn healthy. Aeration involves making holes in the lawn either by pushing a rod into it or by "coring", extracting a plug of soil. By aerating your lawn you provide the following benefits to your lawn and its root system:
Oxygen gets to the roots and the soil allowing it to "breathe"
Organic fertilizers and nutrients get access to the root system
Water is able to better soak the soil and reach the root system
Helps to break up thatch
Tight, compacted soil is loosened up allowing the root system to grow