'Aerating' simply means making holes in the ground by removing plugs of soil. And it's the single most important task you can perform to maintain a healthy, good-looking lawn
. Nothing else comes close! It relieves compaction caused by foot traffic and creates extra pore space in the soil, allowing air, nutrients and water to enter. All of that helps roots to thrive.
Aerate your lawn at least once a year, preferably in the fall. Do it two or even three times each year if you can. The more, the better. You can rent a lawn aerator at any equipment rental store. Get one that will remove plugs of soil rather than one that pokes holes in the ground.