Bags are used for all sorts of things, but when it comes down to it, they are used to carry things. Due to the various things they carry, bags are made of all different kinds of materials. Some people choose their bags based on looks, comfort, or how earth-friendly they are. While some materials, like plastic, are convenient, they are not very good for the environment.
When you go to the grocery store you are asked the timeless question: Paper or plastic? Traditional grocery bags are made of those two materials. However, they are slowly starting to phase out as people become more earth conscious. Both use up valuable natural resources. However, both are fairly effective as bags, which is why they have been around for so many years.
In lieu of the traditional grocery bags, reusable bags are being used. The majority of these are made from recycled cotton, hemp, and recycled Polyethylene Terephthalate. This last material is sometimes referred to as PETE. It is made from recycled plastic, and bags made from these can be used over and over again. Hemp bags are very strong, can carry a lot of weight, and hold their shape well.
Back packs, whether used for school purposes or for camping, need to be able to carrying a lot of weight. For this reason, a mixture of cotton and nylon is typically used to make these bags. Gortex, a thicker type of nylon, is sometimes used in mountaineering backpacks because it helps weatherproof the bag and make it even stronger.
Handbags, or purses, are grouped into the "bag" category by some, because they do essentially the same thing: they help carry things around. Handbags are made by designers, which makes the materials that people use to make them all different. Luxury bags are typically made from leather. This is a durable, stylish material that can be died different colors. It also gives the stiffness that is required in designed handbags. However, some designers still choose to use materials like cotton for their designs.