Cash is the most liquid form of money: physical coins and banknotes in the most narrow sense of the term.
In the everyday meaning of the word, cash is the physical form of currency: coins and banknotes that can be carried on person and used to pay for goods and services immediately.
However, in different contexts, the meaning of cash can expand to include bank accounts and marketable securities such as government bonds. Even less narrowly, in finance, cash includes all currency equivalents that can be liquidated immediately or near-immediately.
Historically, gold and silver coins were for a long time an almost exclusive means of payment across the globe: the scarcity of precious metals ensured their value and their uniformity allowed for simpler accounting.
The emergence of paper money from seventh century CE onwards has led to the gradual detachment of the value of cash from the value of the material it is made of and the ultimate appearance of fiat currencies — like the U.S. dollar and the euro. These are established as money by the decision of the government and have no intrinsic value.
From the 1980s on, societies across the globe have been increasingly moving away from cash, replacing it with debit and credit cards and, more recently, mobile payments. As of November 2020, the global volume of cash comprises roughly $6.6 trillion — just a fraction of $630 trillion to $1.2 quadrillion, which is the total volume of all types of money.