The invisible hand is a metaphor for the unseen forces that move the free market economy. Through individual self-interest and freedom of production and consumption, the best interest of society, as a whole, are fulfilled. The constant interplay of individual pressures on market supply and demand causes the natural movement of prices and the flow of trade. 

The term "invisible hand" first appeared in Adam Smith's famous work, The Wealth of Nations, to describe how free markets can incentivize individuals, acting in their own self-interest, to produce what is societally necessary.