What is dual exhaustion and what does it do?

You mean dual 'exhaust'. That is basically it, two pipes. The idea is similar to a bucket of water and a hose. If you put a hose in the bucket, vacuum the air from one side of the hose and then lower the hose below the bucket. What you get is that the water will pump on its own momentum. Car exhaust works the same way.

In General, large exhaust (souped up rice cars) means you have more power in the upper band of the rpm range, but less power in the lower band.

small exhaust -> more power in the lower rpm range but less power in the higher rpm range.

dual exhaust is basically a compromise between the two. You keep the individual pipes small, but in exchange have several pipes. Result, good midrange power.

Well there are two kinds of dual exhaust. Typically if you see two separate mufflers then that is true dual exhaust but then there are several cars that simply have dual tail pipes, two exhaust pipe ends coming out of one muffler. Camaros will have this a lot of times while Mustangs will have true dual. It can do a couple things to the car. It can change the horsepower and it can change the tone of the exhaust.

Dual exhaust is either having two mufflers or either having pipes running straight from the engine or "straight pipes." If a truck sounds loud and has mufflers then it can either have one muffler or two mufflers and they are most popularly flowmaster. I don't know how but they make the truck seem louder with still having a muffler. I myself have a flowmaster with dual exhaust.

Hope this helps.

Well they dont allow more airflow... because it depends on the size of the muffler... some cars might come with dual exhaust but that is just to quiet it down a bit because if they only put one it would be noisy... i changed mine from 1" dual exhaust outlet to 4.5" dual exhaust outlet and it sure gives you more power but i think i would achieve more power with just a single muffler that is a 4.5" outlet.

dual exhaust is a system that allows more airflow through the system. It's basically for more performance. A car's engine is basically an air pump, and the more air that goes through it, the more power it makes. So, to increase performance, you add larger intakes, exhaust, more displacement, anything that allows the engine to pump more air.

It's just a way to make the car more attractive visually....that's all.

Two exhausts look "sportier" than one.

it just makes it sound more sporty then a single and they look better with 2 tips then just 1. myself, i like them on trucks better then cars.