The Photo Stream will be copied to all devices that have Photo Stream enabled. Though it may take a while depending on connection speeds and internet availability.
When you choose to Copy a photo in the Photo Stream it is placed in the clipboard so that you can go to another app and paste it (if the app allows pictures to be pasted). The photos you Save are copied to the Camera Roll. You can see them if you select the Camara Roll under the Albums tab. The are not removed from the Photo Stream when you copy, and on iOS devices will remain there until:
- 30 Days have passed or
- you exceed 1000 photos or
- you manually delete them.
Photo Stream photos on a computer are only deleted when you do so manually. This is because computers are less likely to run out of storage due to a few thousand photos.
Photo Stream photos can not be placed into an album until you've saved them to the Camera Roll. Albums created in the Photos app do not duplicate the photo, which means if you delete that photo from the Camera Roll, it will also be deleted from the Album. Photos warns you when you choose to delete a photo that is in more than one place.
iCloud: Photo Stream FAQ