As Jock describes, it is an air dam, to help airflow and stability at speed.
It also has a second function. It is usually the lowest part of the car, and designed that if it contacts anything, it makes a lot of noise, when it causes the bumper to vibrate along with it, so frightening the driver into not continuing.
For example, when parking towardsa a kerb, this air dam will contact teh kerb and make noise, before any real damage is done, and hopefully the driver stops before the sump hits something solid. Looks like it might have met this sort of challenge recently, hence the damage.
If you remove it, you need to remember that you may have no warning before something important hits something, so watch where you're going.