Can some one please explain the meaning on the saw films?

I understand there I a deeper meaning in the film more than just killing people, like you should cherish your life an that, but even though I've watched all the films a stupid amount of times they still leave me completly clueless to the whole proper moral to the stories, any advice or information would help so I'd like to thank anyone who answered in advance and apoligies for any spelling mistakes I've made :D