What do the dashboard warning symbols mean?

 

These pictures aren't all from Audi's but you get the idea. Also, you failed to mention what year your car is, so they may not match exactly what you're seeing anyway, but you get the idea.

This one is pretty self explanatory:

Low washer fluid:

Brake pads are thin:

This lovely little combination usually indicates a bad ABS module. The light on the right is also the parking brake idiot light.

In newer A4's equipped with the LCD info screen between the tach and speedo, you might see something like this:

That means your oil level sensor is on the fritz, that same symbol with the word "MIN" in place of "SENSOR" means your oil level is below the minimum level and you should top it off. That same symbol in red with no words means low oil pressure, thats not good. I think thats all of them, but don't hold me to that.