Core aeration consists of removing cores or “plugs” from the grass which promotes a better growing environment for your turf. Core aeration increases air flow and nutrient absorption to the root system; this process alone will produce a healthier grass stand.
Combine this with over seeding in the fall or spring and you are giving yourself the best chance possible for a thick and vigorous lawn. The plugs produced from core aeration are left on the surface to break down which creates a topdressing and increases seed to soil contact. Seed to soil contact is essential when trying to establish turf, so a conjunction of the two gives you a winning combination.