Just purchased the 3axis 200oz.in. hobby CNC kit package and the spec said it comes with 8 unipolar steppers, I believe.

I am quite new with the steppers, but try to access information in regard to how bipolar, unipolar works.... In general, I understood how 4 wire bipolar works, but would anyone can explain how
#23-200-DS8, 200oz-in Dual Shaft, 8 wire work?
I thought that bipolar produces higher torque for the same size with unipoloar. What is advantage in using it anyway?

Thank you so much for explaination, appreciate it.
Jeff.