What do you mean by Line and Staff Organisation?

Line and Staff Organisation:

When the industry grew within size and complexity, the line executives could not carry out properly all other functions as like R and D, distribution, planning, and public relations, legal. It necessitated the employing of special executives to help line executives and they were termed as Staff as they were recruited to perform specialist or staff functions. There line executives keep supervisory authority and control over the work of their subordinates while the staff executives relieve the line executives of specific specialized work and advise them onto matters considered to them. The given figure demonstrates the line and staff organization: