Glossary
Retraction
Retraction pulls filament backward slightly during travel moves to stop the nozzle from oozing plastic where it should not.
Retraction is a slicer setting that tells the extruder to briefly pull filament backward and away from the hotend melt zone whenever the nozzle needs to travel across empty space without printing. That small pullback reduces the pressure inside the nozzle so it stops dripping or oozing plastic onto the part during the move.
Two numbers matter most: retraction distance, how far the filament pulls back, and retraction speed, how quickly it happens. Bowden printers, where filament travels through a long tube before the hotend, generally need more retraction distance than direct drive printers, where the extruder sits right above the nozzle and the melt zone is much closer to the motor.
Too little retraction leaves stringing and blobs at travel points, while too much can grind the filament, wear a groove into it, or cause under-extrusion right after each travel move. A sensible approach is to test one printer and filament combination with a stringing test print and adjust distance and speed gradually rather than copying settings from an unrelated setup.