Scarification is designed to address moss and thatch problems.
Thatch is a dense mat of roots, stems and grass clippings that accumulates between the soil and growing blades of grass. As thatch builds, adequate amounts of vital turf nutrients, including water, oxygen, nitrates, phosphorus and potassium, are unable to reach the root system. Moss then loves to grow on this thatch layer.
Scarification effectively removes thatch build-up by "power raking" the lawn turf. This allows air and nutrients to reach the root system again.