Thatch is formed from the cut grass clippings that fall to the ground under your live grass. This thatch creates a barrier that prevents water and nutrients from fully penetrating your soil, which inhibits your grass from being it's healthiest. Your yard WILL have thatch and need dethatching unless you bag your clippings, rake your clippings or use mulching blades.
Dethatching is the process of lifting and breaking up the thatch layer. This can be done by hand with special "thatching rake" or with a pull-behind tine dethatcher like the one in our videos here. As you can see in the videos & pictures here, the tine dethatcher we use does an excellent job of lifting and breaking up the thatch in your lawn. The best time to dethatch your yard is Fall or Spring, but can be done anytime to allow more moisture and nutrients to penetrate your soil.
We add weights do our dethatcher to make sure it gets deep into your lawn to get under the thatch and lift as much as possible off the soil surface.
You can imagine the barrier all of that thatch would have created if it had not been lifted out from under the live grass.