Most paper bags are made from kraft paper. Kraft paper may be unbleached (brown) or bleached (white) and can be made in a wide variety of strengths or thickness (called "weight" by the industry). 

How the paper is cut and folded determines the shape of the bag. Four basic paper bags are used for packages that consumers buy: flat, square, satchel-bottom, and self-opening. The flat bag is the simplest. It's just a tube of paper with one end folded under and pasted down to form the bottom. This type of bag often is used to hold nuts, candy, and potato chips. The square bag is a flat bag, but adds more paper at the side and tucks the paper to form a side panel, called a gusset. If you thrust your hand inside this bag, the bottom will form a square, creating a roomier bag. The square bag is used in packaging all types of food products, textiles, hardware, and candy. The satchel-bottom bag also is a flat bag, but it has a diamond-shaped, preformed bottom that allows the bag to stand up on its own. The satchel bag is used for packaging such products as sugar, flour, rice, peas, beans, and spices.

The paper grocery bag and many other types of specialty bags are self-opening bags. The square bag is used in packaging all types of food products, textiles, hardware, and candy. These bags have gussets and specially precut bottoms that form a square. The bag is designed to pop open with the flip of a wrist and stand open while being filled. Some retail bags, called duplex bags, are made from two layers of paper. They can be made in any of the styles mentioned above.