Gold is a precious metal which has been sought after by men (and women) for at least 5,000 years but there is also a sting in the tail for this most sought after metal. It is extremely rare. This has led to gold becoming one of the most valuable of metals in the world and the history of mankind. Its importance has been further underlined by governments around the world using gold bullion to provide the asset-backing for the money they issued in the times of early coinage, the value of a coin was actually the amount of gold which it contained the stamp of the treasury or mint which issued it was a quality assurance that the coin really contained that much gold and this spread to the use of gold for other purposes, particularly jewelry and today gold is always stamped with a hallmark.  

It is this link to the financial worth of currency which creates most of the demand for gold today. Paper money is just that paper it is a promise that the bank or treasury department of a nation will pay that value which is promised on the paper (a dollar, 5 dollars, 10 dollars or whatever). It used to be that for every 1 dollar issued as paper, there would be 1 dollar in gold stored at Fort Knox or the Federal Reserve Bank in New York everyone had confidence in accepting the dollar bill simply because the US government had the gold to make sure it held its value. In depressed times, the value of paper would become suspect or in relative terms, the paper money would lose its value relative to other currencies or assets  investors would therefore look to put their money into other valuable assets which would not be affected by the economic recessions and gold was an obvious choice.