What does “schwitzen” mean in a German recipe?

Schwitzen literally means “to sweat,” but in the kitchen it’s a precise technique: cooking vegetables in a little fat over low heat until they turn soft and glassy, without letting them brown. The vegetables release their own water as they cook — that release is the “sweating” — which keeps their flavor mild instead of caramelized.

This pumpkin-soup video uses the technique exactly by the book: onion, garlic, celery, and carrot get geschwitzt for a few minutes in oil before the pumpkin and ginger go in. German recipes more often reach for the related verb anschwitzen for this same technique — gently cooking vegetables in fat until soft without letting them brown — so if a recipe tells you to die Zwiebeln anschwitzen, it means exactly the same thing as schwitzen here.