Thatch is an organic layer of dead and living stems, leaves and roots that develops between green vegetation and the soil surface. Thatch forms as a natural part of turf's growing process. Thatch is caused by overwatering, overfertilizing and always mowing too high.
The pros of thatch are that it provides insulation against temperature extremes and fluctuations in soil moisture, provides resiliency on sports fields to soften a player's impact on the surface and also improves footing. The cons of thatch are an increase in pest problems, blocks sunlight from reaching lower grass blades and prevents water and fertilizer from reaching the soil.
Two ways to remove thatch are by dethatching or aerating. Individuals can determine if their lawn needs dethatching by feeling the lawn, visually inspecting the lawn, and measuring the thatch. A thatch layer of more than three-quarters of an inch means it's time to dethatch. An aerator pulls plugs out of your soil and helps loosen compressed soil in order to allow air and water to reach the roots. Aerating is considered a better way to detach your lawn because it puts less stress on it. To prevent thatch, keep your leaves raked and remove grass clippings after mowing.