I know about the Doppler effect, but I don't know what the Doppler radar uses and what it measures. The student thought it used sound waves on ground stations to measure wind speed. It actually sends a pulse of energy out, then listens, then sends another pulse of energy, then listens, etc. So, we listen for the amount of energy returned from the previous pulse. Rain will bounce more energy back the heavier it is, and hail will return a great amount of energy back.
Snow actually is quite a small energy returner.
We simply view a graphic and can tell where the more intense thunderstorms are located in our area. We can also tell if the particle that returned the energy is moving away or toward the radar - the Doppler effect. In this manner, we can tell the velocity of the particles and if thunderstorms are rotating. These are tough questions to answer for the common person. For professional meteorologists, this is learned in the third of four college years in a meteorology degree program.