It has six monthly economic indicators and two quarterly economic indicators it follows and based on their trend makes the determination if we are in a recession.
The monthly ones are real personal income less transfers, nonfarm payrolls, real personal consumption expenditure, real manufacturing and trade sales, household employment, and industrial production.
For the most part the monthly indicators have been positive. Particularly for the first quarter. That is why many economists don't think we are in a recession now as aside from GDP the numbers are not particularly bad. Especially the labor market.
The two quarterly ones are real GDP and real GDI. Real GDP was -1.6 and -0.9 for the last two quarters. Real GDI on the other hand was 1.8% for the first quarter. The second quarter GDI comes out next month. These two indicators should be the same in theory, but they often aren't. So the committee averages them. The average for the first quarter was slightly positive. Another reason it is very unlikely the committee would say we were in a recession in the first quarter.
The committee defines a recession as a significant decline in economic activity that is spread across the economy and that lasts more than a few months. Though the last part isn't set in stone. The beginning of the pandemic was classified as a recession because activity declined so much, even though the decline only lasted a couple months.