Photo sharing in iOS device, Easy option on share photos with your friends by inviting individually or in group. Like other social apps, users can view each photo, Comment on it and like photos with fun. for that you have to enable/ Turn on photo sharing on iPhone for Easy Photo management and photo sharing only compatible with latest iOS or Mac OS X.
here you can also learn how to accept or view photos on another iOS or Mac device. By accept request for join.
Note: if are you requesting your friends through photo sharing, Both device must be enabled photo sharing option. For iPhone, iPad, iPod Touch or Mac.
Useful: Best photo editing apps
Steps for Enable/ Turn on Photo sharing on iPhone, iPad
Step 1: Head to setting app on iPhone, iPad
Step 2: Next, Tap on iCloud. Then photos.
Under the photos, Enable iCloud Photo sharing toggle by tap on it. Then you can create album or photos group by selecting from camera album (Photos app). 
Once you enabled Photo sharing, Your photo app should be show up cloud icon at beneath of the screen. See below image. 
Steps to Turn Off photo sharing on your iPhone
Note: if are you want stop photo sharing on iOS device or Mac temporary, then You will lost all the past create albums and sharing history from device only (Not from camera roll saved photos or video). in future you re enabled photo sharing you have to create new setup for that, And restore all shared album history.
For Disable or Turn off Go to The settings > iCloud > Photos > iCloud Photo sharing.
How it Works?
After enabled photo sharing for share photos or video, You have to send it on your Friend’s iCloud ID. at the receiving end your friends will get notification on accept for view photo album in the same iOS or Mac running on above configurations. 
More about setup or Turn on photo sharing on iPhone, iPad, Mac FAQs and Your question, read out this apple tutorial, Also share how you like above tips on below comment. Now we are keen what will be the new in iOS 10 photo sharing features?
