One way people learn about organizational behavior is by becoming part of an organization. In fact, most of us learn this quite early, in pre-school or in school, since these are organizations, just as much as workplaces are. We learn by observing what goes on around us in the organization and internalizing what we see, for example, the presence of a hierarchy and the expectations of the organization. We generalize from these experiences, forming our own ideas about organizational behavior. This is pretty much just part of the normal process of socialization. As adults, of course, most of us learn this in the workplace, by the same process, observing and internalizing.
Some of us learn about organizational behavior from a theoretical perspective, taking classes in the subject or reading on our own about it. There is nothing wrong with learning this way, but without the experience of an actual organization, there is nothing to which we can apply the theories we learn.
In order to have a good understanding of organizational behavior, a theoretical grounding and experience with organizations is the optimum. We have difficulty learning anything in a meaningful way unless it connects with something we already have some knowledge of.