What is this news
GDP (Gross Domestic Product) is the total value of all goods and services produced in a country. The growth rate shows how much the economy grew compared to before. Released by National Statistics Institute (INE). This comes every month.
How important it is
This is the biggest measure of an economy's health. Flash/Advance is the first estimate, which gets revised later. This is a High impact event on FxGram: EUR pairs often see sharp moves at this time.
What this data does
Generally, if GDP comes in above forecast, the economy is considered strong and this is seen as a good sign for the currency; if lower, it signals weakness.
This is just general knowledge (textbook), not a prediction for this release. The market may react differently. This is not buy-sell advice.