Imagine for a moment that we're flying in a plane over a large city. We can see factories, banks, schools, hospitals, retail stores, car showrooms, ships and boats at the port, and so on. These are the structures that define the city.
If we look carefully, we'll see things happening within and between these structures. Lorries might be delivering iron ore to the factory, customers might be withdrawing money from banks, students might be sitting exams—it's a busy world down there!
And, if we could look a little closer, we would see that all these people and organizations are involved in meaningful activity with each other. Students receiving assessments from their teachers that will subsequently help them get into college. Banks giving loans to clients who can then move home. Factories making components from raw materials, which are assembled into complex objects by their customers. People buying used cars from dealerships that they use to get them to work...