CPI, or Consumer Price Index, is a measure of the average change in prices of goods and services purchased by households over time. It is used to track inflation and reflect the cost of living for consumers. The CPI takes into account a wide range of goods and services, including food, housing, transportation, and healthcare, and is calculated by comparing the current prices to a base period. This index is an important tool for policymakers, businesses, and individuals to understand the impact of price changes on the economy and make informed decisions.