What is meant by demand? Can you provide examples of a schedule and a demand curve?

Answer:
Demand refers to a relationship between the price of a good (calibrated on the vertical, or y, axis on a graph) and a corresponding quantity demanded (measured on the horizontal, or x, axis of a graph) in a given market area, at a particular time. It is a negative relationship between price, and quantity demanded, as opposed to a positive relationship between price and quantity supplied, which we discuss in another question. For example, a study might show that at $50 a carton, consumers are prepared to buy 20,000 cartons of cigarettes in Halifax, N.S., on a day in July. If the price were $40 a carton, we have a group of consumers who are prepared to buy 30,000 cartons.
When the price has dropped to $30 per carton, consumers are prepared to purchase 40,000 cartons. Given a further price reduction to $20, consumers are willing to buy 60,000 cartons. Finally, when the price is a low $10 per carton, consumers are ready to buy a sizable 90,000 cartons. We use the term "are prepared to buy" to indicate a willingness to purchase, since on one July day, we know that there will likely be only one price available to consumers in the Halifax area, with perhaps a few large retailers offering a discount. Also, the concept of demand suggests that consumers think to themselves, "I want this particular good, I am prepared to buy it today, and I have the cash (or credit) to buy x number of cartons of the product."

Note that opportunity cost, the consideration of the most highly-valued alternative, is, as in most decisions, at work in any buying situation. If the consumer is prepared to pay $40 for a carton of cigarettes, this is a relative price in the sense that the $40 could have bought another needed product, such as a pair of blue jeans. Other useful alternatives are being forgone or, possibly, postponed.

A demand schedule, such as that outlined above and illustrated below, shows various price levels and the quantity demanded that consumers are prepared to buy at any given price. The ceteris paribus assumption is also in play; that is, we are holding all other factors other than price, such as income or preferences, constant for the purposes of this analysis. Here is what Schedule 6-1 will be:

If we put this data on a graph with the price on the vertical axis and the quantity demanded on the horizontal axis, then we have the typical downward-sloping demand curve, which illustrates the social tendency called the Law of Demand—the subject of our next question.