Named after economist John Maynard Keynes, who believed the best way to ensure economic growth and stability is via government intervention in the economy.
When times are good, a government should raise taxes and curb public spending to ensure the public finances are robust. As soon as times get harder, tax cuts to help those still in work should be accompanied by public spending on infrastructure projects, such as schools, road maintenance – maybe even an Olympic village. That keeps people in work even as job losses hit the private sector. If people are kept in jobs they will keep on spending and borrowing, which in turn supports firms and reduces the impact of a recession. So the theory goes.