Introduction to Supply

In theory, supply refers to the quantity of goods that producers are willing and able to supply at various prices over a given time period. Unlike a demand curve which is downward sloping, supply curve would be the total opposite. A common supply curve would be as follows ; 

Price-Supply relationship

Why upward sloping?

Imagine if under a contract, you were given a piece of land. You must produce a combination of potatoes and carrot and maximize your profits. Let say that both of them are priced the same and uses the exact same amount of land per acre to produce a kilo of produce, thus you would be utilizing the land to produce both equal in quantity ( assumes that there is no extra cost involved for both the products ). If the price of carrots were to increase, it would make sense for the producer to shift most of his land to plant carrots hence selling more carrots. Therefore the quantity supply in the market would increase as the price of a product goes up because it is more profitable now than before to produce that product, all others being equal.

In this globalized economy, where there's consumer demand there will be a supply ( of course, the demand must be logical and attainable at the same time ). To which comes first is still debatable. According to Say's Law ( Named after Jean-Baptiste Say ) , supply creates its own demand. The idea is that when people produce any commodities (supply) and earn money from it, the money is useless if it is not used. Therefore money gained from selling a product is used to buy another product which they want (demand). Though this law became a conflict for the two main schools of economics, the classical and Keynesian as the former believes that production will lead to a growing economy while the Keynesian argues that growth comes only from increased demand.