Not all toys are made the same way, even if they all seem to be made of the same kind of plastic. The exact type of plastic used will depend on the specific toy, but some types are more common than others, such as polyethylene, poly vinyl chloride and polypropylene.
One of the sturdiest types of plastic on the list, polyethylene comes in two forms: low- and high-density. The kind you see with toys is the thicker and sturdier high-density, whereas low-density polyethylene is more commonly used for trash bags and similar items. Usually, this plastic doesn't get used inside the toy itself; rather, this is what much plastic packaging is made of. The next time you can't get that Marvel or DC figure out of its plastic prison, at least you'll know your enemy's name.
Poly Vinyl Chloride
Much more commonly known as PVC or vinyl, poly vinyl chloride is more rubbery than it is solid, though that doesn't mean it's not also durable. Many of the toy cars you'll find that feature tires that appear to be rubber are actually made using the plastic PVC. Ongoing debate exists regarding the safety of additives and gas used in this toy material, but you probably won't have anything to worry about if you don't chew your toy's tires.
Polypropeylene Use in Toys
As the similar name might suggest, polypropeylene (PP) features similar properties to polyethylene; both are polymers, but the former comes from propylene instead rather than ethylene. As a cheaper alternative, there are some benefits associated with choosing this polymer in toy manufacturing, but it's not without drawbacks; polypropeylene varies considerably in durability, so a cheap toy that uses it might actually just be a cheap toy.
Acrylonitrile Butadiene Styrene
Typically found in Hasbro's Transformers toy line and in LEGO, acrylonitrile butadiene styrene (ABS) is a sturdy and tough plastic. Although it doesn't happen to every toy made with this type of plastic, gold ABS materials are known to suffer from flaking. Polycarbonate also makes an appearance on Transformers as windows; this transparent plastic resembles compact discs -- because it's the kind used to make them.