What is crochet shaping?
Shaping will add a curve to your work (e.g. to fit the body) but edge increases alter the shape of a flat piece (e.g. to make a shawl triangular). Chevron stripes sweater has internal shaping at waist and hips.
Why is my crochet sweater so heavy?
Now without tying myself in technical knots, crochet is thicker because you are effectively creating two layers of yarn when you wrap it around your hook – notice your crochet stitches have yarn doing different things on each side of your stitch.