A straight front view shows the face of a product and hides its depth; a side view shows the profile and hides the face. The three-quarter view sits between them and shows both, which is why it is the usual angle for shoes, bags, furniture and boxed products: the toe and the side, the front panel and the gusset, in one image.
On a model, a three-quarter pose turns the body slightly, which shows the side seam, the sleeve and the way a garment falls from the shoulder. It reveals less of a chest print than a front view does, so the two are used together. In a gallery, the three-quarter image normally follows the plain front view.