Changes

The demand curve is always '''''downward sloping''''': the higher the sales price, the '''''lower''''' the quantity the public is willing to buy.  Few people will buy a candy bar if it costs $5: if that price is lowered to $2, then more people will want to buy it, and if its price is lowered to $1, then even more will want to buy it, and if its price is lowered to 50 cents, then the demand by the public for that candy bar will be greater still.  As the price for something goes down, the demand goes up.  That results in a downward-sloping demand curve:  as the price goes down the slope of the curve, the '''''quantity''''' demanded (sought) by the public goes up.

The demand curve is always '''''downward sloping''''': the higher the sales price, the '''''lower''''' the quantity the public is willing to buy.  Few people will buy a candy bar if it costs $5: if that price is lowered to $2, then more people will want to buy it, and if its price is lowered to $1, then even more will want to buy it, and if its price is lowered to 50 cents, then the demand by the public for that candy bar will be greater still.  As the price for something goes down, the demand goes up.  That results in a downward-sloping demand curve:  as the price goes down the slope of the curve, the '''''quantity''''' demanded (sought) by the public goes up.

The supply and demand is the most basic relationship in all of economics.  They are independent of each other, but are placed on the same graph so that it becomes easy to find "equilibrium": the point where supply and demand have the same value for their price, and the same value for their quantity (the point of the intersection of their curves).   

The supply and demand is the most basic relationship in all of economics.  They are independent of each other, but are placed on the same graph so that it becomes easy to find "equilibrium":<ref>The dictionary (Merriam Webster's Collegiate 10th Edition) tells us that an "equilibrium" is "a state of balance between opposing forces" - in this case, the opposing forces of the supplier wanting a higher price, and the public (consumers) wanting a lower price.</ref> the point where supply and demand have the same value for their price, '''''and''''' the same value for their quantity (the point of the intersection of their curves).   

If the price is higher than the equilibrium price, then the lower demand will force sellers to lower the price until the public buys the unsold goods; if the price is lower than the equilibrium price, then the higher demand will encourage sellers to increase their price (and their profits) to sell what they have.  Those market forces push the final price to the point where the supply curve intersects the demand curve, which is where the price and quantity for the supply side are equal to the price and quantity for the demand side.

If the price is higher than the equilibrium price, then there will be unsold goods due to less people wanting to pay the higher price.  The sellers will then need to lower their price in order to sell these leftover or unsold goods, and that forces the price downward to the equilibrium price.  Conversely, if the price is lower than the equilibrium price, then the sellers will not have enough goods to satisfy the higher demand by the public.  The sellers will then increase their price (and their revenue) to take advantage of the higher demand.  These market forces both above and below the equilibrium price are what push the final price to the point where the supply curve intersects the demand curve.  At this point the price and quantity for the supply side are precisely equal to the price and quantity for the demand side.

The supply and demand curves usually look like this:

The supply and demand curves usually look like this: