fill in flash is used to help see your emphasis but still allows the shadows to stay in the pictures. You can uses the fill in flash by turning on your flash. When your emphasis is in a shadow with a bright background you use fill in flass to see your subject.
People are use to seeing things in the anlge that they see everyday. They look at things straight ahead. looking from a different point of veiw makes the picture more interesting. For example, look at an object for a birds or worms point of view.
Simplicity helps the veiwer focus on the emphasis. Sometimes a picture can have too many objects and make the picture clusterd. Having the background nic e and simple makes the emphasis stand out.