Photo Stream is a great way to save or share the photos from your iPAd to another Apple device or to a computer, and to share photos with friends and family. If you’re into photos, you should check it out and see if it suits your needs. This artilce will give you some general information about Photo Streams.
Apple has recently increased the limits on how many photos can be shared in a given period of time. Most people do not come close to the old limits. However, if you are on a trip and suddenly have hundreds or thousands of photos to upload, the limits may be important.
For example, you can now upload 25,000 photos in a given month, or 1000 photos in a given hour. (Note that you can still only have the last 1000 photos available in the cloud.) This article from Apple gives all the details, including what happens when you exceed a limit. It covers both your own photo stream, and any shared photo streams you are using. My siblings and I find it a great way to keep in touch!