What are the advantages of line and staff in an organization?

Having line and staff within one's structure usually represents savings on personnel costs in an organization, in addition to the advantages described in the previous responses.  This is because the staffing functions often comprise more highly paid employees, employees who can then serve all functional departments, rather than having to staff each functional department with its own "experts" in the areas that typically make up staff functions.  For example, a legal department or an information technology department usually consists of highly educated and/or trained employees who command higher salaries than many of those in the line functions.  If production, marketing, research and development, and distribution divisions had to maintain their own legal and information technology experts, this would add substantially to personnel costs, with no additional benefit to the company, since many of the staff functions would not be full-time work for a particular line department, but just right as they are allocated over all line functions.