iCloud Shared Photo Library lets you... "Share photos and videos seamlessly with up to five other people, so everyone can collaborate on the family’s collection and enjoy more complete memories. With iCloud Shared Photo Library, family memories are in one place for everyone to enjoy at any time, even if you’re not the one who snapped the shot or edited the photo."
To set up the feature, launch the Settings app, tap Photos, then tap Shared Library.
The setup wizard will then let you add participants, choose which photos will be moved, and preview the shared library.
You can watch Apple's demo of how iCloud Shared Photo Library works below...