Young people need to be prepared for adulthood so that they are ready to use their genitals properly and safely. Madame shows them the technique of intercourse, teaches them how to suck and swallow and demonstrates by personal example how to get an orgasm. The young men really liked the lesson - they absorb all the knowledge with genuine interest. The adult woman seems quite happy with the result. I have no doubt they will repeat the lesson on their own!
The shooting is clearly amateur, the lady doesn't want to advertise herself and is wearing huge glasses all the time. Is she skinny? I would rather say she is athletic with a very nice figure. It's a pity they fuck in such unsanitary conditions. If they would have taken a hotel room, they could have made a more interesting video.