GDP is the market value of all final goods and services produced within a country's borders in a given time period (usually, within a year). By saying "final goods and services," we exclude "intermediate goods and services," which are produced in order to help make something else. For example, the shirt I'm wearing is a final good, but the cotton used to make the shirt is an intermediate good.
A recession is a prolonged decline in economic activity throughout the economy. During recessions, a country's GDP falls and its unemployment rate rises.
Disposable income is the income available to be spent by actors in the economy. It is usually defined as total income plus transfers minus taxes. Transfers refers to payments individuals receive from the government, for instance social security checks.
The real interest rate measures the cost of borrowing (or, equivalently, the return for lenders) after accounting for inflation. In math terms, the real interest rate equals the nominal interest rate minus the inflation rate. So, for example, if someone has a car loan with an interest rate of 7% and if inflation is 5%, then the real interest rate is 2%.
A country has a trade deficit if the value of the country's exports are less than the value of their imports. In other words, a trade deficit occurs when a country buys more goods and services from the rest of the world than the rest of the world buys from them. Expressed as an equation, the value of the trade deficit equals imports minus exports.
