You’ve all heard the term before, countless times no doubt. But what does it really mean? Well, the biggest clue is in the name. MACROeconomics is a branch of economics that looks at the economy as a whole, specifically, at its structure, performance, and behaviour. It does so by considering aggregate changes to phenomena like gross domestic product (GDP), inflation, price indices, national income and unemployment rates. 

Marginal revenue (MR) measures the change in total revenue that occurs when a firm increases output by one unit, i.e., it is the extra income (or revenue) generated by selling one additional unit.

Marginal utility is the change in wellbeing (or change in total utility) that a person experiences if they consume one additional unit of a good or service. One of the most basic ideas in economics is that the consumption of goods and services changes our level of satisfaction or happiness (also referred to as utility). Often, we measure this change in satisfaction in monetary terms. If, for example, we want to know how much the wellbeing of a person changes if we give them a book (for free), we can simply ask this person how much he or she is willing to pay for the book.

A market is in equilibrium if at the market price the quantity demanded is equal to the quantity supplied. The price at which the quantity demanded is equal to the quantity supplied is called the equilibrium price or market clearing price and the corresponding quantity is the equilibrium quantity.

Standing in contrast to macroeconomics, microeconomics looks at the choices made by economic actors - be they people, firms, or whole industries -  and how they affect the allocation of scarce resources. Primarily, this involves investigation into why goods and services assume different values and understanding how changing economic conditions can alter the decision-making of economic actors. 

A monopoly describes a market in which there is only one firm and it does not face any competition. A monopolist is a firm that offers a unique product or service without close substitutes and therefore does not have any competitors. This means that the monopolist faces the entire market demand and each customer interested in buying the product can choose whether to buy from the monopolist at the respective price or not to buy at all.