Entrepreneurs are efficient creatures, always trying to find a better way to do something. When you hit a snag on your journey and recognize the need to learn more about a given topic, you'd rather not spend the time taking a class or reading a whole book. You really want a friend to just "give you the 101" on the topic at hand.
Peer-to-peer learning is powerful, because it scales rapidly. Everyone is an expert at something and a newbie at many other things. By belonging to a group with complementary skills you can accelerate your personal growth. All 101 sessions are informal crash courses, and in return for acquiring free knowledge, it is expected that sometime in the future you will be the one sharing your expertise.