What Is The Private Sector In Sport?

The private sector in sport is comprised of commercial companies, opposed to government(public) sector or voluntary sector.
This sector is interested in commercial and financial success of the companies ahead of sporting achievements.
Companies that would be included in the private sector would include Adidas, Nike, Powerade ect.

Get involved in sport so that they are able to make money out of it,

Please will someone help me describe the private, public and voluntary sectors in sport economically, socially and politically.....?