Answer to Question 1
In the Real Business Cycle Theory, changes in output are driven by changes in technology, which change aggregate supply. The changes in technology can be driven by new inventions, natural disasters, changes in the public's preferences for work, discoveries of natural resources, or government regulations and taxation which affect both firm's and worker's incentives to produce.
Answer to Question 2
Investment goods include the purchase of capital by firms and the purchases of homes by households. A car purchased by an individual is consumption, a car purchased by IBM is an investment good. Inventories are counted as an investment good.