It stands for the Defensive Specialist who is often times the middle back. They almost always play back row.
Defensive Specialist Sometimes called a libero
setter
Setter
libero
dual screen
Digital System
no
Ds stands for "double screen'' as in the two ds screens.
There are usually 2 referees in a volleyball game. One is on the stand and one is on the floor.
Dual Screen. Simple.
mb stands for middle blocker.