Span of control refers to the number of subordinates a manager can effectively oversee. A narrow span of control means a manager oversees few subordinates, resulting in a tall organizational structure. A wide span of control means a manager oversees many subordinates, resulting in a flat structure. Centralization concentrates decision-making authority at the top levels of management, while decentralization delegates authority to lower levels of management. Centralization allows for coordination and leadership from the top but slows decision-making, while decentralization facilitates faster decision-making but distributes power throughout the organization.