Plastic of course is a broad term for a host of different materials, which is part of the problem. Most of it is polyethylene, which itself comes in different versions, though they are chemically the same (in basic composition). Milk jugs are PE. Then there is polypropylene, milk jug caps are PP. You don't want PE mixed in with PP if you are recycling.
Then there is PET for short, which makes up the bottles of water and Coke we buy. The caps are PP. PET also makes up the polyester in the shirts we wear (polycotton is a blend).
Packaging material is polystyrene foam, something very different from the above chemically. It takes up a lot of volume when it is 'foamed". Dow Chemical doesn't like it when we call packaging material Styrofoam, but we do. They are in Michigan anyway.
And there are "tons" more types, but those are the main ones, unless I'm forgetting something which is likely. Polyurethane is one more that can be hard or soft depending on which kind it is. Those spray cans we use to insulate tight areas are polyurethane foam. A lot of the hard plastic that makes up stuff is PU.
IF you can get a stream that is source separated, you have something you can recycle rather easily, but if it is a mixture, good luck. It does no good if YOU separate the items nicely and they get thrown on the same truck.