$1.$ The distinction between a change in demand and a change in quantity demanded. If the entire demand curve shifts $($e$.$g$.,$ more would be purchased at any given price$),$ that is a change in demand. If you change the price of Good X and the quantity demanded for Good X changes, that is a change in quantity demanded, NOT a change in demand. This point is often misstated by non$-$economists $($e$.$g$.,$ Investopedia gets a lot of its economics definitions wrong$).$ To get a change in demand, you need something other than the price of that good to change. A change in income, a change in the price of a complementary good or a substitute good, or a change in tastes and preferences can shift a demand curve. That would be a change in demand. There are some videos in Module $2$ that dive deeper into this topic.

$2.$ The distinction between positive economics and normative economics. If a statement is saying what is better or 'good,$\text{'}$ or 'bad,$\text{'}$ then it is a normative statement.

$3.$ Know the importance of private property rights for a well$-$functioning economy.

$4.$ 'Scarcity' is not the same as 'shortage.$\text{'}$ Scarcity is what gives rise for the need for economics $($the study of the allocation of scarce resources$).$ If the amount of a good or service that society wants, when the price is zero, is greater than what is available, then that is a scarce good $($or service$).$ If we set a price above the market$-$clearing price, there would be a surplus, but the good$/$service would still be scarce. If we set a price below the market$-$clearing price, there would be a shortage. 'Scarcity' is essentially what is happening at a price of zero. Charging a higher price is one way $($among many$)$ to allocate a scarce good. In the first discussion question, the surfable waves in Lunada Bay were a scarce resource, which were allocated based on the threat of violence. If the waves were not scarce, then there would be no competition for those waves.

$5.$ Competition is inevitable if you have scarce goods$/$services$/$resources$.$ However, having said that, a person$/$firm will usually prefer less competition to more competition.

$6.$ Middlemen are important and provide their services in their own self$-$interest. Note that we can also say that the sellers provide their goods and services in their own self$-$interest, too.

$7.$ When will people trade? Will people with identical tastes and preferences trade if they are given different starting bundles of goods?

$8.$ What are transaction costs? Don't think of them as those extra charges you might have to pay to withdraw money out of an out$-$of$-$network ATM machine. Instead, think of the non$-$monetary costs involved in researching products, discovering prices, and consummating a deal$/$purchase$.$

$9.$ Consumer surplus is the difference between the maximum that you are willing to pay and what you actually pay.