Two iphoto windows on the same Mac

The other day I downloaded a bunch of photos and created several albums to/on my iMac from my iPhone, iPad and camera. At the same sitting, I inserted a stick and placed two photos into an album. Today I went back into iPhoto to do some more organizing and to download more photos off the stick, only to find none of those newly downloaded photos, and no new albums. I also noticed that the window back ground was a different colour than before. Just to see what would happen, I plugged my iPad back into Mac, and voila, a second iPhoto window appeared, with a different set up and a different colour back ground, and all the photos and albums I downloaded were in that second window, and included all the photos and albums that were on the first iPhoto window that has always been on my Mac. I am at a complete loss and am hoping there is a simple solution as I am not that tech savvy. Has anyone ever encountered this!