Dethatching is a removal process of tightly intermingled layer of living and dead stems, leaves, and roots which accumulates between the layer of actively growing grass and the soil underneath. Thatch is a normal component of an actively growing turfgrass, and as long as it is not too thick, it can increase the resilience of the turf to heavy traffic. Thatch develops more readily on high-maintenance lawns than on low-maintenance lawns.
We usually do dethatching once in a year to get the the layer and give the grasses more air, light to grow faster.