In this context, PPP stands for Paycheck Protection Program:
The Paycheck Protection Program (PPP) is a $669-billion business loan program established by the 2020 US Federal government Coronavirus Aid, Relief, and Economic Security Act (CARES Act) to help certain businesses, self-employed workers, sole proprietors, certain nonprofit organizations, and tribal businesses continue paying their workers.
The article you linked actually explains this, but oddly, it's "below the fold".
The bill, likely to be almost identical to the one that failed in the Senate in September, includes funding for the Payroll Protection Program (PPP), extra unemployment benefits, money for schools, and liability protections for businesses.
I had to click the "Story Continues" button near the bottom of the page to find this sentence.