What are these lines on side of mouth!Watch
I think pretty much all people will have them when smiling. But some people have them at rest too.
They are called nasolabial folds and develop from age and laughing/smiling a lot! Some people naturally have more defined ones due to genetics, and you can see how they are all different shapes. Some curve in almost a semicircle, whereas others seem to drop down with little shape at all.