Definition: Alan Greenspan is the chairman of the board of governors for the Federal Reserve. He's entrusted with controlling the money supply and interest rates in order to keep the economy stable and inflation under control.
Advice: Alan Greenspan holds one of the most important positions in the US Government. The decisions he makes ultimately control the economy. This is why investors closely watch what he says. When he chooses to lower rates, money becomes "cheaper" and the economy heats up with economic activity. The problem is that this comes with a price: inflation rises as well. In order to combat inflation, Greenspan raises rates, which unfortunately slows the economy.