What is money? A question borne from my ignorance of the subject. Money is not one subject but a whole series of subjects. Money is, amongst other things, about trust in the value of things, about exchanging in currencies, about measuring the capacity to own property.
Think of the kissi pennies. Or cowrie shells as earliest chinese currency in use between 16th-8th century BC. The largest ever bank transfer note in US currency was a $100,000 note in 1934 featuring Woodrow Wilson. The UK equivalent is a £100 million note called titan found only in the vaults of the Bank of England. The history and continuing importance of money is rather intriguing.