This app is just a little help for all those people, who like to easily share their old photos via photo stream. Since you cannot share your old photos via photo stream with just your iPhone or iPad - here is the solution. Press the button, then choose your photos you want to have in photo stream and let the app do the work for you.
What does the app ?
It just saves all the pictures you have chosen again to your photo library. If you are using already photo stream, all your chosen photos will then "appear" in your photo stream and will be copied to your other devices which are using photo stream.
After this you have the chosen photos doubled in your device where you used the app. You then can manually delete the photos with the Photos app (the built in app from Apple).
Only photos can be synced.
Location data on pictures will be lost in the new copied pictures.