In maslow's hierarchy of needs, needs refer to the desire of a person to be accepted by people and groups important to that individual.

The answer is:  "belongingness" . 

       "In Maslow's Hierarchy of Needs [theory],  belongingness   needs refer to the desire of a person to be accepted by people and groups important to that individual."

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.