Markets
For many economists (but not for Marxists) the key question about any economic system is whether it is a market system or not.
Markets have a long history in human societies. Stone tools made of Swiss stone, dating from the early "stone age," can be found very widely in the eastern hemisphere. They were almost certainly spread over thousands of miles by barter exchange, thousands of years ago. But, until recent centuries, markets affected only a small part of the goods and services people enjoyed. Most people produced for themselves most of the goods and services they used, within the household or the local group, without the products passing through markets. In that sense "market economic systems" are relatively new.