whats the difference between a ...
 

strut bar and a sway bar? What do they do? Sway bars allow you to corner faster with less body roll, correct? ...or is that strut bars. Just wondering . thanks
~Adam

strut bars connect at the top of the chassis, in the front of the car
 

they bolt into the strut towers at the top, a 15 minute DIY job. It increases chassis rigidity and makes the car a lot more stable and predictable through turns but as far as I could tell didn't influence oversteer/understeer at all. Sway bars connect at the bottom of the suspension, and I can't really comment because I don't have any but a front sway alone will cause understeer and a rear sway alone will cause oversteer.

Re: whats the difference between a ...
 

I don't have a strut bar on my A4, but I do have one in my '91 GTi and it has helped strengthen and made the body much more rigid.

A sway bar is a stabilizer bar and adds stiffness (!)

yep, and by stiffening the connection between the two sides of the car
 

in cornering, it will reduce the ability for those two sides to move independently and make the car more predictable but lose overall traction (ie, why a rear sway will cause the back end to step out in hard cornering)

Depending on the car (non-A4s), you could also get one in back.