The tan sao is described as a palm up hand. It is an attacking hand oriented forward.
encyclopaedie
The gaan sao is a hand move that reminds of a plough. It moves downwards following the orientation line.
The jut sao is executed with the inner part of the wrist and serves as a preparation for further attacks like a punch or a fung hao.
The scissors gaan sao is to be considered equally as defensive or offensive move. It protects the whole upper body from waist to head.