850 Exhaust: Bosal vs. OEM/Stock.

[Hanzi]

I have noticed that some complete exhaust/mufflers actually have what looks like a second muffler in the straight piece that is between the over the axle section and the tail pipe, but Bosal's does not. (95 850 wagon)
1)What is that: a second muffler, a resonator- what?
2)Is Bosal's substantially louder or different as a result of putting a straight pipe there?

Thanks,