Inflation means an overall increase in the prices of goods and services. It is a decrease in the value of a currency. There are three types of measurement, Core Inflation, CPI, and WPI. Core Inflation is a measurement of non-volatile goods such as food and non-precious metals. It leaves out goods like oil because oil's price is subject to wild fluctuations. CPI is the most common measurement, using a market basket of goods and measuring their price from a point in the past (a CPI of 100 is arbitrarily the same price level for 1982-1984). Thus, the equation is (Price of most recent market basket/price of same market basket in 1982-1984) X 100. The 100 is to give us the number we normally see. WPI is Wholesale Price Index. It is a measure of wholesaler's prices and is generally considered a pre-cursor to what CPI will be (as it takes time for goods to read the consumer).