The simplified version is that I will send a small series of energy pulses through your body and it will "bounce" off of you and return information about your physical condition to me. You won't feel a thing, it's non-touch and completely painless.

It is simply the manifestation of one's will to understand and observe certain information. To remain impartial, it returns information piece by piece rather than as a whole. That way I won't look at the results as "you are fine" or "you are injured" - I will be able to make that judgement based on the knowledge of your heart rate, respiratory rate, temperature, etc.