how will volcker rule affect the banks?

[muscleman]

http://dealbook.nytimes.com/2012/05/10/goldman-moves-to-comply-with-volcker-rule/

 

I still don't understand how volcker rule applies to the banks. Does this mean banks cannot trade derivatives, or it even means banks cannot hold common stocks of other companies?

Investment banks like GS generate most of its profits from trading. I still don't understand what trading it conducts. I know it does some market making.

What exactly will GS be affected in terms of trading department?