Confused about duplicate files...

I've had my MacBook for about 7 months now, and I am noticing that my finder is getting a bit cluttered. One thing that will help me a lot is figuring out which photos are stored twice on my hard drive. The problem is, I can't tell. For example, when I search Photo Booth in the finder a bunch of photo booth pictures appear, but a folder also appears that contains every single one of my photo booth photos. Now, are the ones that aren't stored in the "master" folder duplicates, or are they necessary? Sry if this is hard to understand. I tried my best. Thanks.