The methods in which humans have exchanged one good for another has always been direct and as of recent history, done through a traditional "buy -sell" model.
This could change.
2/ What is Barter(ing)?
In essence, bartering involves the provision of one good or service by one party in return for another good or service from another party - Investopedia
This is the means of transaction that our ancestors used till the advent of currency (2,000 BCE)
3/ The Status-Quo: Currency
USD, EUR, JPY, RMB, BTC, ETH...
We earn currency through the provision of goods and services and in turn, use that currency to purchase goods and services we desire.