Chains vs. Plates?

Bigger Stronger Leaner Competitive Bodybuilding
1

In a couple of articles and posts here i have heard people recommend the use of chains for deadlifts etc. I was wondering if someone can plz tell me how chains are different than just adding plates?

2

Here you go:

Accomodating Resistance by Dave Tate:
http://www.t-nation.com/readTopic.do?id=459390