Supposedly, a transaction involving cash and an apple was performed. In the transaction, there was an agreement that one dollar could be exchanged for an apple. Once completed, the transaction detail is recorded in a ledger. The transaction worked because the one dollar of value is represented by a physical currency, both parties recognized and trusted having been created by a government to facilitate trade.
When it comes to digital cash, the situation becomes more complicated.
Imagine it’s not that easy to prove a transaction without involving trusted intermediary such as banks. This becomes much more complicated with virtual currency like bitcoin.
– An explanation of how blockchain works by Standard Chartered Bank