Gold is the oldest form of money dating back millennia; Up until 1971 the US Dollar was linked to physical GOLD held in Fort Knox in America, and all other world currencies were linked to the US Dollar thereby linking them indirectly to GOLD. This is known as a “Gold Standard”.
The old Dollar bills had written on it "REDEEMABLE IN GOLD ON DEMAND AT THE UNITED STATES TREASURY"
In 1971 the US, under President Nixon, unilaterally ended its gold standard, and the era of ‘fiat’ or paper currency began. The word “fiat” is derived from Latin, meaning “a decree or order from a person in authority”.
Currency today has no intrinsic value. Governments print currency at will (called Quantitative Easing) to solve deeper problems. The result is that the value of your paper currency in your pocket today gets diluted or eaten away by the increase in currency supply, creating inflation, meaning your currency is worth less tomorrow than it was yesterday.
In 1971 gold was valued at US$35 per ounce. Today it is valued over 5,000% higher.
Since 1971 until today the US Dollar (and every other fiat currency) has lost about 99% of its purchasing power or value
The Graph below tracks the US Dollar from 1900 until 2010 highlighting significant global events, and the effect on the value of the currency. Recent excessive money printing since 2010 will significantly further negatively impact the dollar going forward. (https://ginifoundation.org/kb/fiat-currency-graveyard-a-history-of-monetary-folly/)