Iphone photostream/camera roll

Hi, just a noob question. If I take a photo, does my photo get saved both in my photostream and camera roll? If it does, the photo in my photostream will remain in there for 30 days while the one in the camera roll is permanent until I delete it correct? When the photo in my photostream gets deleted automatically after 30 days, will the photo on my PC also be delete? Any help is appreciated, thanks!