What does the red exclamation point symbol mean in an Audi A6?

I noticed a red exclamation point symbol on my Audi A6 dashboard. What does it mean and what should I do about it?

The red exclamation point symbol usually indicates a problem with your vehicle's braking system. It's important that you get your car checked by a certified technician as soon as possible.

The red exclamation point symbol can also appear if your car's brake fluid levels are low. Check your brake fluid levels and top up if necessary.