A contingency fund is cash set aside by a company or an individual to be used in the event of unforeseen need. Unfortunately, unforeseen needs happen all the time, from the bill that was not expected to the loss of a major client. A contingency fund example is a savings account with up to six months worth of revenue.
Set up your contingency fund with liquid, spendable, money. Cash under a mattress would be a good contingency fund example where the cash is easily spendable. However, cash under a mattress would be susceptible to theft, fire, or flood; or some other sort of loss. Cash in an FDIC insured account would be a better idea, as long as the amount of money is below the maximum insurable FDIC amount.
Gold, stocks, bonds, or other investment vehicle would not be liquid money as they must be converted to cash in order to be spendable. The time involved for conversion may be a factor as the emergency event may be time critical.