Saws are very handy when you need to cut through something that is made of a strong material, like wood or plastic. Sometimes those materials are too thick and hardy for a simple hand saw, so you opt for a power saw. These guys are able to cut through much more durable materials like thick trees or even building composites. Just keep in mind when cutting plastic, that if you blade does not have  a speed setting and generates too much heat, the small plastic shavings can melt and fuse together inside your cut, while gumming up your blade as well.