The exhaust system in your vehicle is an extremely important system. As your engine is running, there will be gases and noise that are produced. In order to get rid of these gases and noise, your exhaust system will move them away from the vehicle. Otherwise, you would notice these things in your cabin.
A part of your exhaust system that is at the very end of the situation is a muffler. The muffler will muffle any sounds that are coming from your engine. This is also where the gases will come out.
If your vehicle is in need of repairs in this area, you may notice a strong odor coming from your vehicle while it runs. You could also experience an increase in cabin noise while you're driving along. It's a good idea to have these areas checked out before the problem gets worse.