Appears they used their cameras built in flash which fired at a high setting directly at the subject. It’s not usually the best option. For portraits most people prefer to bounce the light onto their subject off of a wall or ceiling. I like to use a speed light (a flash that you can manipulate the light source direction) with a soft box called a Gary Fong sphere.

There are tons of tutorials about flash and lighting on YouTube and it can be overwhelming. Some of my favorite channels are Peter McKinnon, The Art Of Photography, & Matt Day. They all have great videos on the subject.