What does the border-radius property do in CSS?

The border-radius property in CSS is specifically designed to alter the appearance of an element by rounding its corners. When you apply the border-radius property, you can define how much curvature is applied to each corner, allowing for a more visually appealing design or to achieve a certain style. This property can be applied to all kinds of elements, including divs, images, buttons, and more.

Adjusting the border-radius can create effects such as circles when applied uniformly to a square element or elliptical shapes when different values are provided for each corner. The value can be specified in pixels, percentages, or other CSS length units, giving designers flexibility in their designs.

The other options listed do not accurately describe the purpose of the border-radius property. For instance, adding shadows, setting border widths, or changing the position of an element pertain to different CSS properties and functionalities.