Recycling is defined as the process of converting used materials into new materials. Not every type of material can be recycled; those materials most commonly recycled are aluminum, cardboard, glass, paper, plastics, and steel. And contrary to what many believe, recycling is typically not one to one, meaning that material that gets recycled isn't necessarily converted to that same material. Thus, old glass doesn't necessarily end up as new glass, and old plastics don't necessarily end up as new plastics.