Currently Being ModeratedOct 4, 2013 6:03 AM (in response to priester68)
Photo stream (now called My Photo Stream) is a syncing service, used to sync photos from one device to another. It's not intended to be used as a storage service (Always sync photos to a computer to archive them). Only devices logged into the icloud account can get copies from the stream servers (and photos in the stream are only kept for up to 30 days, after which they are deleted from the servers).
A Shared Photo Stream is one in which other users can view your photos without having to log into your icloud account.
You need to decide what you want to do with photos and then pick the right service. Try googling Photo Stream, and Shared Photo Stream to learn about the two in more detail.