In 1923 Germany a loaf of bread cost about 250 marks in January and 200 billion marks by November. Workers were paid twice a day so they could spend before prices climbed again. That extreme case shows what inflation really is: a sustained rise in the average level of prices across an economy, which means each unit of money buys less than it did before.
To track inflation, economists build a Consumer Price Index (CPI). They pick a fixed basket of goods a typical household buys — food, rent, fuel, a haircut — and price that same basket month after month. If the basket cost 100 dollars last year and 104 dollars this year, prices rose 4 percent. The CPI turns thousands of separate price changes into one clear number.
Not every price moves for the same reason, so analysts split inflation in two ways. Headline inflation includes everything in the basket. Core inflation strips out food and energy, whose prices swing wildly month to month, to reveal the steadier underlying trend that policymakers actually target.
Where does the upward pressure come from? Demand-pull inflation happens when spending outruns what the economy can produce. Too much money chases too few goods, so sellers raise prices. Cost-push inflation comes from the supply side. When a key input like oil gets more expensive, firms pass the higher cost on, and prices rise even though demand has not changed.
Inflation is not just an abstract number. It imposes real costs. Firms waste resources reprinting price lists, a nuisance economists call menu costs. People waste time and effort managing cash to dodge the erosion, called shoe-leather costs. Worse, inflation redistributes wealth. It quietly punishes savers and lenders while rewarding borrowers, because debts get repaid in cheaper money.
The opposite problem can be just as dangerous. Deflation is a sustained fall in prices. It sounds pleasant, but it pushes shoppers to delay purchases while they wait for lower prices, which starves firms of sales and can deepen a recession.
At the far extreme sits hyperinflation, where prices spiral out of control, as in Weimar Germany or Zimbabwe in 2008. Money loses meaning, savings vanish overnight, and the economy reverts to barter. That nightmare is why central banks guard price stability so fiercely.