Real gross domestic product
Real gross domestic product (real GDP for short) is a macroeconomic measure of the value of economic output adjusted for price changes (i.e. inflation or deflation). This adjustment transforms the money-value measure, nominal GDP, into an index for quantity of total output. Although GDP is total output, it is primarily useful because it closely approximates the total spending: the sum of consumer spending, investment made by industry, excess of exports over imports, and government spending. Due to inflation, GDP increases and does not actually reflect the true growth in an economy. That is why the GDP must be divided by the inflation rate (raised to the power of units of time in which the rate is measured) to get the growth of the real GDP. Different organizations use different types of 'Real GDP' measures, for example the United Nations UNCTAD uses 2005 Constant prices and exchange rates while the FRED uses 2009 constant prices and exchange rates, and recently the World Bank switched from 2005 to 2010 constant prices and exchange rates.
GDP deflator
It is often useful to consider implicit price deflators for certain subcategories of GDP, such as computer hardware. In this case, it is useful to think of the price deflator as the ratio of the current-year price of a good to its price in some base year. The price in the base year is normalized to 100. For example, for computer hardware, we could define a "unit" to be a computer with a specific level of processing power, memory, hard drive space and so on. A price deflator of 200 means that the current-year price of this computing power is twice its base-year price - price inflation. A price deflator of 50 means that the current-year price is half the base year price - price deflation. This can lead to a situation where official statistics reflect a drop in prices, even though they have stayed the same.