Photo Library-Photo Stream-Camera Roll , whats the difference between these
Camera Roll contains photos you have taken on your device, accessible locally. 

Photo Stream is a set of photos synced to all your devices, and only takes the last 1000 photos or from the past 30 days, whichever comes first. Photo Stream does not affect your iCloud storage. 

(iCloud) Photo Library is where photos can be uploaded to, outside of the photos you take on your iDevice (so DSLR photos can be in Photo Library) and it does affect and consume your iCloud storage.