The Austrian business cycle theory as developed by Mises and Hayek is explained. First business cycles are distinguished from the normal market process. After doing varying time preferences of individuals are explored and integrated into a loanable funds framework. Then an expansionary scenario based on increased savings is outlined and contrasted with an unsustainable expansion is induced by monetary policy of the central bank. The latter accordingly leads to malinvestment of resources and to a recession. Lastly, the Austrian business cycle theory is contrasted with a very rough outline of Keynesian understandings.