Explainer-SEC eyes Wall Street reforms. What is 'PFOF'?

Go back to Explainer-SEC eyes Wall Street reforms. What is 'PFOF'?
(NASDAQ: HOOD) Delayed: 119.02 -1.8 (1.49%)
Previous Close $120.82    52 Week High $ 
Open $121.63    52 Week Low $ 
Day High $121.90    P/E N/A 
Day Low $117.53    EPS $ 
Volume 8,347,727       

Charles Schwab (NYSE: SCHW) Delayed: 99.53 +0.04 (0.04%)
Previous Close $99.49    52 Week High $37.71 
Open $99.52    52 Week Low $21.51 
Day High $100.61    P/E 127.60 
Day Low $98.77    EPS $0.78 
Volume 1,997,854       

(NASDAQ: VIRT) Delayed: 41.92 --0 (-0%)
Previous Close $41.92    52 Week High $23.97 
Open $41.92    52 Week Low $12.35 
Day High $41.92    P/E N/A 
Day Low $41.92    EPS $0.00 
Volume 578,831