This picture is a perfect illustration of exactly the best way to
properly fall a large tree. I wished I had seen it before I cut my
first one down.
The notch helps guide the tree where you want it to fall, and prevents
it from sandwiching your chain saw, which is a bad thing and can be
very dangerous.
Chainsaws are louder than most power tools and require adequate ear
protection if you want to avoid long term hearing damage.