This gives good light on your subject but leaves enough exposure on the background to provide a sense of context. The flash will also recharge faster and use less battery power. Sometimes you can get more depth in flash shots by bouncing the flash off a white ceiling. This lights up the whole room. Too high a ceiling will not reflect much, and a colored ceiling will give a color cast to color shots.
Exposure is hard to judge.
Some automatic flashes have sensors that look ahead in the same direction as the camera while the flash head swivels up. These can be trusted to some extent, although they still look for the first object that reflects light back. So does practice. When you use bounce flash, be careful to turn the flash far enough up. If you do not, you will have part of the scene lit by direct flash, and part not.