The yoke is a shirt's shoulder area that extends from the neckline to the sleeves. Its purpose is twofold: first, it provides structure and support to the garment; second, it creates a visual interest or design element. Yokes can be either functional or decorative, or sometimes both.
Most commonly, yokes are found on button-down shirts. The yoke helps to distribute the weight of the fabric and prevent pulling at the buttons. It also reinforces the seams where the front and back panels of the shirt are joined together.
Yokes can also be seen on dresses, skirts, and even pants (though this is less common). Again, their primary purpose is to provide support to the garment and distribute its weight evenly. In some cases, they may also serve as a design feature, such as when they're made from contrasting fabric or feature ruffles or other embellishments.