The first time you set up iPhoto on your Mac to work with your iCloud account, you’ll see this window, which lists two different options – My Photo Stream and iCloud Photo Sharing.
These two options work in completely different ways, but you need to get them set up properly first.
Read:

Open iPhoto’s Preferences panel and click the iCloud tab.
As you can see, My Photo Stream and Photo Sharing are listed as two separate options, so you’ll need to click and select both options in order to use them within iPhoto.
Read:

My Photo Stream works well, but has some limitations. It can, for example, only share photos between devices that are linked to your iCloud account.
Also, video clips will have to be imported into iPhoto by hand. There is a way around this, though, which is where Photo Sharing comes in.

A shared photo stream lets you share images and videos with other people.
At the moment, these photos are stored in My Photo Stream, but we can share them with some friends by selecting the photos we want and then clicking the Share button down in the bottom-right corner of the screen.

Photos stored in My Photo Stream are separate from the permanent iPhoto library that’s stored in your Mac’s Pictures folder. Before you can share these photos with anyone else, you need to import them into your iPhoto library.
The snowboarding photos will then show up as a new event in the main Events list.

Next, iPhoto shows you where your images are in your Photo library, and then gives you two options for sharing them: My Photo Stream and New Photo Stream.
We want the latter, and as shared photo streams can also contain videos, we’ll select the snowboarding video clips shown here.

You can now enter the names of the people that you want to share your photos with.
iPhoto will find their details in your Contacts app and send them email invitations.

If your friends have iCloud accounts of their own then they’ll automatically receive a notification telling them that they’ve been invited to share your new photo stream.
Here’s the invitation that popped up on Karen’s iPad, and anyone logged into iCloud on their Mac will receive a similar invitation, too.

Here are the photos and videos transferred to Karen’s iPad. We selected the Subscribers Can Post option when we set up this shared stream, so she can also see an option in the lower-left of the screen that lets her add photos and videos.
Tapping on any individual photo will allow her to add comments.

But, of course, not everyone has an iCloud account, which is where the Public Website option comes in handy. iPhoto will create a link for the website and send that link to the people who can’t see the shared photo stream using iCloud on their Mac, PC or iOS devices.
We also have a number of other articles about sharing photos. Read the following: