We are sometimes frustrated when less ambient light so that we trouble to get a high shutter speed to freeze the subject of the photo. When we meet at such times, we can use the flash (either on camera or external Speedlites).
The flash has a flash duration is quite short, usually only 1/1000-1/20000 seconds. Flash duration is the duration of the flash illuminates the subject of the photo shine.
Well because the short duration of light, then the subject of the photo we can be frozen even if we choose the shutter speed is relatively slow (eg 1/60 sec) in a rather dark environment.
In a brightly lit environments like a outdoors in the sun, this trick does not apply because shutter speed will slow even motion capture subject of the photo, instead of freezing it.
Therefore, if for example we want to freeze the subject of the photo in a relatively dark environment, we can use the flash.
