In March 2020 the world economy fell off a cliff. Factories shut, flights stopped, and millions lost their jobs in a matter of weeks. No single supply-and-demand diagram could capture it. To understand a shock that size, you have to study the economy as one giant system. That is macroeconomics — the branch of economics that looks at the whole economy at once rather than one market at a time.
Microeconomics asks how the price of coffee is set. Macroeconomics asks bigger questions. How fast is the economy growing? How many people are out of work? Are prices rising too quickly? It answers them with aggregates — economy-wide totals like total output, the number of jobs, the average level of prices, and the rate of growth.
The first tool you will meet is the circular flow of income. Picture money flowing in a loop. Households sell their labor to firms and get paid wages. They spend those wages buying goods from the same firms. The firms use that revenue to pay workers again, and the loop continues. This simple diagram shows how spending by one person becomes income for another.
Real economies are not that tidy. Some money leaks out of the loop, and some gets injected in. Leakages are money that leaves the spending stream — savings, taxes, and money spent on imports. Injections are money that enters from outside — investment by firms, government spending, and money foreigners pay for exports. When injections match leakages, the economy is in balance. When they do not, output rises or falls.
A full economy has four players: households who supply labor and spend, firms who produce and invest, the government which taxes and spends, and the foreign sector which trades. Together they answer the three basic questions every society faces: what to produce, how to produce it, and who gets the result.
Finally, you will see how societies organize the answers. A command economy lets the state decide everything. A free-market economy lets prices and private choice decide. Almost every real country is a mixed economy — markets do most of the work, but the government steps in to provide roads, schools, and a safety net.