A live photo captures what happens 1.5 seconds before and after you take a photo and is normally switched on by default. However, should you wish to disable this feature, click the yellow dot at the top of the camera window.
It is worth noting that, when a live photo is taken, it gives you many more editing options not available from an ordinary shot. For example, you can slide up on the photo and add different effects such as putting it on a loop or adding a long exposure.
