What is Demand? Not, what you wish to have! What you wish to have is simply your wishful thinking or desire. Demand is what you wish to buy against a particular price. It is the desire to buy a commodity (or a particular amount of a commodity) at its particular price, at a point of time.
Important thing to remember is that demand for a commodity cannot be discussed independent of price of the commodity.
Ask your mother: How much of fruit (say apples) she wishes to buy? Pat should come the reply: It depends on the price of apples. Higher the price of the commodity, lower the purchase of the commodity. It is a standard relationship between price and purchase, on the assumption that other things (other than price and purchase of the commodity) do not change.
It refers to demand for a commodity by an individual buyer in the market. ?Ram buying 10 shirts at a price of Rs. 500 per shirt? is an example of individual demand.
It refers to total demand for a commodity by all the buyers in the market. If Ram and Shyam are the only two buyers in the market, and both of them are buying 25 shirts at a price of (say) Rs. 500 per shirt, market demand would be: 25 shirts at a price of Rs. 500 per shirt. Or it could be 30 shirts at a price of (say) Rs. 400 per shirt, and so on.
Note: Both in case of individual demand and market demand, the inverse relationship between price and purchase holds goods. In fact, buying more at a lower price and buying less at a higher price is a phenomenon related to human psychology. We shall discuss more about it in the subsequent sections.