S1 visa for my mother

Hi there,
I'm a South African citizen working on a Z type in China. I would like to invite my mother(also a South African citizen) over to the PRC on an S1 type to stay with me for the duration of my Z type, she will be my guest and will not work here at all. What is the difference between the application for a S1 type and the S2(S2 type is too short). Thank you!