The last time the economy was in a recession was 2001 and 2008, after the tech bubble burst. Members of the Business Cycle Dating Committee explained the requirements for a recession in a statement.

A recession is a significant decline in economic activity spread across the economy, lasting more than a few months, normally visible in production, employment, real income, and other indicators. A recession begins when the economy reaches a peak of activity and ends when the economy reaches its trough.

The US Is Officially in a Recession — Are You Surprised?