Look at it this way:
By wearing the right clothes for your body shape, you’ll “fill out” and sometimes slim down areas, creating a proportional body shape with no heavy point that “interrupts” the eye. By simply choosing the right cut and length you’ll make a wide butt (and hips and thighs), boyish hips and a full torso look less noticeable.
You goal is to create a visually balanced yet feminine body – making it look like your bust and shoulders are at the same width as your hips.
Example of how to balance out and flatter an apple and rectangle body shape:
So for example, if your hips are greatly wider than the shoulders then you’ll have to add more volume to your top half (Fashion trend: strong shoulder). Or if you have a straight waist you’re going to have to find clothes that will add dimensions to your upper and lower part, making your torso look narrower in comparison. And the list goes on. You basically don’t always have to resort to dieting and hiding your body. As long as you appear symmetrical you’ll look great!
And of course, knowing what flatters your body shape makes shopping so much easier because you can steer yourself in the right direction in what you should buy! You’ll save lot time and money.