iCloud Photo Sharing is part of Apple's iCloud service and lets you create Photo Streams that you can share with friends, family, coworkers, or whoever else you'd like. Other iPhone and iPad users can invite you to their shared Photo Streams as well. You can quickly enable or disable iCloud Photo Sharing on iPhone and iPad in just a few taps — here's how!
How to turn iCloud Photo Sharing on and off on iPhone and iPad
Launch the Settings app.
Tap Photos & Camera.
Turn On or Off the option for iCloud Photo Sharing.
Open the Photos app. The Shared tab in should now be in the app's navigation menu between the Photos and Albums tabs.
Alternatively, you can also tap on iCloud and then Photos within the Settings app and you'll get to the same place laid out in the steps above. Either method does the same thing.
You'll need to have iCloud Photo Sharing turned on in order for someone to be able to invite you to a stream. So if you aren't receiving invites, it's a good idea to follow the steps above and ensure you have the feature turned on. Keep in mind people you send invites to will need to have iCloud Photo Sharing enabled too. By default, the feature should be on, but if it isn't, the steps above can help you reconnect to your family and friends.