What Does "Quantity" Represent When Looking at Supply and Demand? There are several possible scenarios involving changes in supply and demand that people are supposed to memorize in AS Economics. For example, when Either Demand OR Supply Move on Their Own:


Rising Demand - Increase in Qty - Increase in Price
Falling Demand - Decrease in Qty - Decrease in Price


While price is pretty self explanatory in every situation, I have yet to fully understand what "Quantity" represents. 

What does Quantity mean in these examples?

Does it mean "Equilibrium Quantity"? If so, can somebody please explain how the "Quantity Demanded" and "Quantity Supplied" are related to each other, and how the theory behind quantity as a whole relates to/ties in with each of the examples above?
Each curve simply shows the amount of goods that producers would supply at given prices and how many units of goods consumers would demand at all the different prices. Let's say the price of wooden chairs would be 5 million Euros. Producers would want to supply a large quantity of wooden chairs, since they're so profitable. Consumers would likely demand very little though. However since no one suppliers want to sell more than people want to buy the price will have to change and will not stay there in equilibrium. We only have an equilibrium when all parties agree, otherwise transactions don't take place. That's one intuitive way of thinking about it if it helps you.

The quantity at which suppliers want to supply exactly as much as consumers demand and consumers want to demand exactly as much as suppliers want to supply is given by the intersection of the two graphs. In this case neither party is unhappy with the outcome (both agree on the quantity to buy and sell). This means we are in equilibrium (i.e. no one wnats to change behavior). That one point is the equilibrium quantity.

Note that consumers cannot buy more than producers are willing to sell and vice-versa. If that would be the case, then they would have to change somthing, which means we wouldn't be in equilibrium. 

So in short: 


The Demand curve shows the quantity demanded. 
The Supply curve shows the quantity supplied.
For the two curves we have several not easily observed hypothetical quantites. One quantity for each possible price.
The intersection is the observed equilibrium quantity.