1769-L33ER Banks of modules

Hi guys,

I was looking for how many slots I use for 1769-L33ER CPU and I found out " 16 1769 modules 2 banks of modules ". 

When it says a bank of modules, what does it mean? does each bank need to have a power supply?

and if it does need a power supply, do i need to count it as one slot? 

Thanks guys !