The presser foot pressure is the pressure exerted by the fabric presser with the presser foot on the fabric and the feed dog. It can be adjusted continuously using an adjustment wheel or adjustment screw on the arm of the sewing machine. The adjustment wheel or adjustment screw acts on a pressure spring, which exerts a targeted force/pressure on the fabric presser.
Source:
Schlums, Ulla; Dressler, Heike; Decker, Sonja (2022), Fertigung Bekleidung, 1. Auflage, Haan-Gruiten: Verlag Europa-Lehrmittel, S. 22