How does a C4 work/shift?

Can someone please run down the transmission shifts for me?

What happens when the rear band engages/releases? What happens when the rear clutch engages/releases?

What happenes when the front band engages/releases? What happens when the front clutch pack engages/releases?

I basically want to know how the tranny works... How does it shift from 1-2-3 and R? What is happening internally with the components?

Thanks in advance.