Precious metals are among the most stable, and most profitable, investments one can make. For thousands of years, having a store of gold on hand was effective protection against poverty and, in eras such as the present where fiat currency is the norm, it has proven an excellent hedge against inflation. Precious metals, though gold and silver are the best known, include several other potential investments, as well. Gold and silver, however, are the most ancient in their usage.
Gold and silver bullion is a very popular investment. This may be purchased outright, in the form of coins or bars, or it may be purchased in the form of titles and certificates that guarantee ownership of a stock held in a bank or other secure facility. Either way, there are few more reliable investments one can make. Precious metals are not assigned an arbitrary value. They all have practical applications and are priced, in part, based on how rare those metals are in the world.
As a good example of this, consider how valuable copper would be if it were as rare as gold. Gold and silver can be used for many of the same applications as copper but their rarity makes them better suited to investment and as a store of wealth. Silver, for example, is a much better conductor of electricity and heat than is copper. Because metals such as gold and silver do have real-world applications, it is their value as a resource that particularly determines their tremendous worth.