High G shale shaker and shale shaker both belongs to sieving equipment. They do not have distinguish difference.
Shale shaker is mainly used for solids control, to seprate solids from drilling fluids. Followed shale shaker, usually desander or desilter.
High G shaker is one kind of shale shaker with a bigger G force. It is mainly used in waste mangement field, to further separate particles from drilling cuttings. High speed centrifuge usually followed high G shaker.