Compare positive reinforcement and negative reinforcement.

Positive reinforcement works by presenting a motivating/reinforcing stimulus to the person after the desired behavior is exhibited, making the behavior more likely to happen in the future. For example: A mother gives her son praise (reinforcing stimulus) for doing homework (behavior).

Negative reinforcement occurs when a certain stimulus (usually an aversive stimulus) is removed after a particular behavior is exhibited. The likelihood of the particular behavior occurring again in the future is increased because of removing/avoiding the negative consequence.

For example: Joe presses a button (behavior) that turns off a loud alarm (aversive stimulus)

In both positive and negative reinforcement, the target behavior is encouraged. The method of encouragement is the difference between the two. In positive reinforcement, a pleasant consequence is added as a result of the behavior. In negative reinforcement, an unwanted or unpleasant consequence is removed as a result of the behavior.

an informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.