What are the main features of line, staff, and informal organizations?

"Group cohesiveness is the degree to which group members want to stay in the group and tend to resist outside influences. An informal organization is the network of connections and channels of communication based on the informal relationships of individuals inside an organization. A line organization is an organizational structure with direct, clear lines of authority and communication flowing from the top managers downward. Line positions are all positions in the organization directly concerned with producing goods and services and that are directly connected from top to bottom. A line-and-staff organization is an organizational structure that includes both line and staff positions."