What is bridge mode? What is benefit of keeping asm in bridge mode

Dear friends,

 

We have asm configured in bridge mode at our new customer.but why asm to configure in brigde mode? What's the benefits & limitations.

 

Please help me as no strong document found on this. I will also appreciate if you help me understand bridge mode,transparent mode & routed mode.benefits & limitations of all three modes.

 

Thanks.