Gauze is a loosely woven, almost translucent fabric that's used to bandage wounds. If you get a bad burn, a doctor might clean it and cover it with gauze.
In medicine, gauze has several uses. Sterile gauze is usually kept in a sealed package, to ensure that it's perfectly clean. It can be used to clean cuts, scrapes, and burns, and also acts as a large bandage. There is also a non-medical fabric called gauze that's used in light, warm-weather clothing. The word's origin is mysterious — one guess traces it to the Arabic gazz, or "raw silk."