As Joseph says, Lesson can be similar to using the New York City subway (underground) and train system. I am told a NYC native usually figures out a way in the first week how to get from their house to their work place. There are lots of ways to do it, each step by itself is simple. Once someone figures out one of the ways, they tend to be happy and do not vary their route and timing. They may miss some interesting bits or variety but that is not their goal
I will avoid comments on HP and Lesson. HP being one of those bits I do not use.
Chris