Adam Smith, the father of modern economics, sought to demonstrate that markets (and economies) pre-existed the state, and hence should be free of government regulation. He argued (against conventional wisdom) that money was not the creation of governments. Markets emerged, in his view, out of the division of labour, by which individuals began to specialize in specific crafts and hence had to depend on others for subsistence goods. These goods were first exchanged by barter. Specialization depended on trade, but was hindered by the "double coincidence of wants" which barter requires, i.e., for the exchange to occur, each participant must want what the other has. To complete this hypothetical history, craftsmen would stockpile one particular good, be it salt or metal, that they thought no one would refuse. This is the origin of money according to Smith. Money, as a universally desired medium of exchange, allows each half of the transaction to be separated.
As Orlove noted, barter may occur in commercial economies, usually during periods of monetary crisis. During such a crisis, currency may be in short supply, or highly devalued through hyperinflation. In such cases, money ceases to be the universal medium of exchange or standard of value. Money may be in such short supply that it becomes an item of barter itself rather than the means of exchange. Barter may also occur when people cannot afford to keep money (as when hyperinflation quickly devalues it).
Modern barter and trade has evolved considerably to become an effective method of increasing sales, conserving cash, moving inventory, and making use of excess production capacity for businesses around the world. Businesses in a barter earn trade credits (instead of cash) that are deposited into their account. They then have the ability to purchase goods and services from other members utilizing their trade credits – they are not obligated to purchase from those whom they sold to, and vice versa. The exchange plays an important role because they provide the record-keeping, brokering expertise and monthly statements to each member. Commercial exchanges make money by charging a commission on each transaction either all on the buy side, all on the sell side, or a combination of both. Transaction fees typically run between 8 and 15%.
Another advantage of bartering is that you do not have to part with material items. Instead, you can offer a service in exchange for an item. For instance, if your friend has a skateboard that you want and their bicycle needs work, if you are good at fixing things, you can offer to fix their bike in exchange for the skateboard. With bartering two parties can get something they want or need from each other without having to spend any money.
In a small economy where individuals specialize in trades, they may find the process of setting up a centralized currency and maintaining it an unnecessary burden in order to trade. One option may be to use a commodity to exchange value between parties that want to trade goods or services and this is why gold and silver have been useful forms of currency in many cultures and times. Another option may be to use a barter system to trade.
In Canada, barter continues to thrive. The largest b2b barter exchange is Tradebank, founded in 1987. P2P bartering has seen a renaissance in major Canadian cities through Bunz - built as a network of Facebook groups that went on to become a stand-alone bartering based app in January 2016. Within the first year, Bunz accumulated over 75,000 users in over 200 cities worldwide.