Short answers, pulled from the story.
Macroeconomics is the branch of economics dealing with the performance, structure, behavior, and decision-making of an economy as a whole, including regional, national, and global economies. It studies aggregate measures such as output or GDP, national income, unemployment, inflation, consumption, saving, investment, and trade.
Macroeconomics focuses on large-scale phenomena and aggregate variables across an entire economy, while microeconomics studies markets and decision-making at a smaller level such as individual firms or consumers. The two are the most general fields in economics, and the divide is institutionalized because their methods and outcomes of interest differ.
Macroeconomics as a separate field is generally recognized to have begun in 1936, when John Maynard Keynes published The General Theory of Employment, Interest and Money. The terms macrodynamics and macroanalysis were introduced by Ragnar Frisch in 1933, and Lawrence Klein used the word macroeconomics in a journal title in 1946.
The three central macroeconomic variables are output, unemployment, and inflation. Macroeconomists also distinguish three time horizons, the short run, the medium run, and the long run, and the openness of an economy, since theory separates closed economies from open economies.
The expenditure method captures GDP by aggregating four main components of spending: consumer spending, government spending, investment, and net exports. Transfer payments such as welfare or social security are excluded because they are not a final good or service.
Since World War II, Keynesians, monetarists, new classical, and new Keynesian economists shaped the field, with Milton Friedman reviving the quantity theory and Robert Lucas introducing rational expectations. By the late 1990s these strands merged into dynamic stochastic general equilibrium models, a new neoclassical synthesis used by many central banks.
Central banks conduct monetary policy mainly by adjusting short-term interest rates, either directly or through open market operations, which moves investment, consumption, asset prices, exchange rates, and ultimately aggregate demand and inflation. Most developed-country central banks follow inflation targeting, keeping medium-term inflation close to a target such as 2 percent.