A feature of Apple's iCloud service that synchronizes photos on Apple mobile devices, Macs, PCs and Apple TVs. When a photo is taken on an iPhone, iPad or iPod, it is uploaded to iCloud and automatically shared on the user's other Photo Stream devices and desktops. Photos do not count against the user's iCloud storage limit.
Automatically or Manually Upload
Apple's iPhoto and Aperture applications can be configured to automatically upload imported images to Photo Stream, or photos can be selectively uploaded from Macs and PCs. Up to 1,000 images are maintained for 30 days, and after 1,000, new images delete old ones. For permanent storage, images must be copied to the user's mobile camera roll or a desktop machine. See iCloud