The goal of this assignment was to get you to try out using filters on your camera.
In your case you’ve used a polarizer.
In simple terms, polarizer filters essentially have laser etched lines on them to take certain parts of the light spectrum and shoot them out to the side, away from your camera’s sensor. These lines are too small to see but they’re very good at diverting light.
Given that, one thing you should use polarizers for is removing reflections. For example, if you have to shoot something through glass (out a window you can’t open etc) you can use this filter to remove the reflection on the glass’ surface.
You may have to play around with the filter and rotate it until you have done so.
Polarizing filters can also darken skies, and add saturation to your photos. So they’re great for landscape photography.