It is pretty funny feature on iPhone. Live photo is not just motion picture but it can merge pictures taken at one picture. And it makes like ling exposure photo.
It has other options, such as loop and bounce. I wonder how many apps support motion pictures. Long exposure is just one taken picture and you can upload on Instagram as well.
When seeing live photo, swipe it and select option you like. Easy.
It is really tricky feature which makes you professional photographer.