Apple’s ‘Live Photos’ are great: “your iPhone records what happens 1.5 seconds before and after you take a picture.” As far as I can recall, Apple’s camera app on the iPhone defaults to Live Photos on.
What if you don’t want to always take a Live Photo? “From the Camera app, tap the Live Photos button to turn off Live Photos. A slash through the Live Photos button means that the feature is off.”
“[But] The Camera app turns Live Photos on again automatically.” “[Thankfully] To keep Live Photos off permanently, follow these steps: Go to Settings. Tap Camera > Preserve Settings. Make sure that the switch next to Live Photo is turned on.”
The information here about Live Photos is from Apple’s support page: Take and edit Live Photos.