What is the 'revolving door' in American politics?

A quick definition of the 'revolving door' concept is the employment cycle in which individuals who work for governmental agencies that regulate interests eventually end up working for interest groups or businesses with the same policy concern. This happens however because governments hire industry professionals for their private sector experience and in order to gain political support from their private firms. The lobbying industry, in turn, hires people out of government positions to gain personal access to government officials and get inside information.