How do you add a border to an element in CSS?

Adding a border to an element in CSS is accomplished using the border property, which allows you to specify the border's width, style, and color. This property directly applies a border to an element, making it a fundamental aspect of design when enhancing the visual separation between elements on a web page.

The border property can be combined in a single declaration—such as border: 1px solid black;—or can be defined individually using shorthand properties like border-width, border-style, and border-color. By using the border property, you can control various aspects of how an element's border appears, providing flexibility and precision in your styling.

Other options do not achieve the same effect. For instance, the margin property is used to create space outside an element, while padding is for space within an element. The outline property, although it also adds a line around an element, behaves differently than borders, as it does not affect the element's layout and is not part of the box model.