First, plastic is collected and taken to a recycling center, where it is "sorted out". When plastic is sorted out, symbols have to be printed on every recyclable plastic product used. There are two types of plastic: "polyethylene" and "polymer". There are two kinds of polyethylene plastic, too: "high density polyethylene" (HDPE), and "low density polyethylene" (LDPE). HDPE plastic is usually used to make furniture, and LDPE plastic are usually things like milk jugs, plastic and grocery bags.