You can call it free fall with elegance or flying - its to escape from enemies and to catch its small prey like birds.
Its able to flatten the body like ribbon and fall even 300ft. It is able to stop when it wants by anchoring on to the trees with tail.
Chrysopelea, or more commonly known as the flying snake, is a genus that belongs to the family Colubridae. Flying snakes are mildly venomous, though the venom is only dangerous to their small prey.
Paradise tree snakes are usually called as flying snakes, They actually glide through the air.Just flattened their body and glide through air..Also called as gliders.
i hope this link will help you in understanding the mechanism.