GDP (Gross Domestic Product)
GDP measures the value of all goods and services produced in a country over a period. Its growth shows the health of the economy.
GDP is usually released quarterly. In the US, the BEA publishes an advance estimate about a month after the quarter ends, followed by two revisions. The US figure is annualised, whereas the eurozone and the UK publish a non-annualised quarterly change.
Two consecutive quarters of contraction are often cited as a sign of recession, even though that is not an official definition everywhere.
GDP is a lagging indicator: it describes the past. Markets often prefer leading indicators such as PMIs. It can still trigger big moves if it is far from expectations.