A market is any one of a variety of systems, institutions, procedures, social relations and infrastructures whereby parties engage in exchange. While parties may exchange goods and services by barter, most markets rely on buyers offer their goods or services (including labor) in exchange for money (legal tender such as fiat money) from buyers.

For a market to be competitive, there must be more than a single buyer or seller. It has been suggested that two people may trade, but it takes at least three persons to have a market, so that there is competition on at least one of its two sides.
However, competitive markets rely on much larger numbers of both buyers and sellers. A market with single seller and multiple buyers is a monopoly. A market with a single buyer and multiple sellers is a monopsony. These are the extremes of imperfect competition.

Markets vary in form, scale (volume and geographic reach), location, and types of participants, as well as the types of goods and services traded. Examples include:
* physical retail markets, such as local farmers' markets, which be held in town squares or parking lots on an ongoing or occasional basis, shopping centers and shopping malls
* (non-physical) internet markets (see electronic commerce)
* ad hoc auction markets
* markets for intermediate goods used in production of other goods and services
* labor markets
* international Foreign exchange market and commodity markets
* stock markets, for the exchange of shares in corporations
* artificial markets created by regulation to exchange rights for derivatives that have been designed to ameliorate externalities, such as pollution permits (see carbon trading)
* illegal markets such as the market for Illegal drug trade, arms trafficking or Copyright infringement

In mainstream economics, the concept of a market is any structure that allows buyers and sellers to exchange any type of goods, services and information economy. The exchange of goods or services for money is a Financial transaction. Market participants consist of all the buyers and sellers of a Good (economics) who influence its price. This influence is a major study of economics and has given rise to several theories and economic models concerning the basic market forces of supply and demand. There are two roles in markets, buyers and sellers. The market facilitates trade and enables the distribution and allocation of resources in a society. Markets allow any tradable item to be evaluated and priced. A market emerges more or less spontaneously or is constructed deliberately by human interaction in order to enable the exchange of rights (cf. ownership) of services and goods.

Historically, markets originated in physical marketplaces which would often develop into — or from — small communities, towns and cities.