I shoot natural light 99% of the time for my portrait sessions, but if you ever see me at a wedding you will likely see me using a large flash unit mounted to my camera. It's called a Speedlite. I notice guests looking at me funny and whispering, "...Why is the flash pointed straight up or behind her? Does she know what she is doing?" - okay, okay, not really....but I'm a mind reader and I know that's what they are thinking ;) Ha! Here is the thing about flash. Flash rarely looks good when pointed directly as someone's face (unless it's difused by an umbrella, softbox or something else). When you see a photographer using a flash that fires at the ceiling, a wall or other surface, they are likely "bouncing" the flash. The flash units that we use are quite powerful and will distribute light off of the surface that we are bouncing from onto the subject(s) that we are taking photographs of. Why do we do this instead of just pointing it forward? When pointed forward, the flash can and likely will blow out skin (no one wants to look like a ghost), create harsh shadows, and what we call pin-lights in the eyes. This is why we use an external flash instead of the one that pops up off of the camera (my camera and most other professional level cameras don't even HAVE pop up flash for this very reason!) So, next time you see me or another photographer using a flash on our camera that isn't pointed at a person, you will know why. There are a million and one other ways of using flash (off camera, special diffusers that mount on the flash while on the camera, the large brackets that pull the flash away from the actual camera body, etc) but I use bounce flash the most.
For good measure, here is a shot that utized the bounce-flash method. No harsh shadows, no overly bright spots on their faces, and nice, natural skintones and colors.