By far the most influential metric on the price of gold is the daily economic information coming out of the worlds markets. Gold has historically always been a "safe haven" type of investment. Like real estate and cash, it is a place to put your money if things aren't looking good elsewhere. When money is pulled out of the stock market it generally flows towards these types of investments, but in 2008 when the stock market and the real estate market experienced simultaneous crashes, gold seemed like the only safe play and, in turn, began its dramatic gains in price.
Inflation is the theory that over time, the value of money will always go down as prices go up. While the average price of a house isn't $40,000 like it was in 1975, the number of gold bars it would take to buy the same house is pretty consistent: $40,000 worth of gold in 1975 would be worth a little over $310,000 today.
This means that no matter what the market is for gold, in the long run it's always better than holding cash without earning any interest on it. While gold doesn't pay interest, its price does generally track the rate of inflation or better. https://www.a1mint.com/shop/